<PAGE>

                                                                    EXHIBIT 10.2

                             WILLBROS GROUP, INC.,

                                   AS ISSUER,

                                      AND

                              JPMORGAN CHASE BANK,

                                   AS TRUSTEE

                           -------------------------

                  UP TO $70,000,000 AGGREGATE PRINCIPAL AMOUNT

                                       OF

                    2.75% CONVERTIBLE SENIOR NOTES DUE 2024

                            -----------------------

                                   INDENTURE

                           DATED AS OF MARCH 12, 2004

                             ---------------------

<PAGE>

                               TABLE OF CONTENTS

<TABLE>
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                                                                                                       PAGE
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<S>                                                                                                    <C>
ARTICLE I DEFINITIONS AND INCORPORATION BY REFERENCE...............................................      1
    Section 1.1.      Definitions..................................................................      1
    Section 1.2.      Incorporation by Reference of Trust Indenture Act............................     12
    Section 1.3.      Rules of Construction........................................................     12
    Section 1.4.      Acts of Holders..............................................................     12

ARTICLE II THE SECURITIES..........................................................................     14
    Section 2.1.      Form and Dating..............................................................     14
    Section 2.2.      Execution and Authentication.................................................     15
    Section 2.3.      Registrar, Paying Agent and Conversion Agent.................................     16
    Section 2.4.      Paying Agent to Hold Assets in Trust.........................................     16
    Section 2.5.      Holder Lists.................................................................     16
    Section 2.6.      Transfer and Exchange........................................................     17
    Section 2.7.      Replacement Securities.......................................................     18
    Section 2.8.      Outstanding Securities; Determinations of Holders' Action....................     18
    Section 2.9.      Temporary Securities.........................................................     19
    Section 2.10.     Cancellation.................................................................     20
    Section 2.11.     Persons Deemed Owners........................................................     20
    Section 2.12.     Additional Transfer and Exchange Requirements................................     20
    Section 2.13.     CUSIP Numbers................................................................     25

ARTICLE III REDEMPTION OF NOTES....................................................................     25
    Section 3.1.      The Company's Right to Redeem; Notice to Trustee.............................     25
    Section 3.2.      Selection of Notes to Be Redeemed............................................     27
    Section 3.3.      Notice of Redemption.........................................................     27
    Section 3.4.      Effect of Notice of Redemption...............................................     28
    Section 3.5.      Deposit of Redemption Price..................................................     28
    Section 3.6.      Notes Redeemed in Part.......................................................     29
    Section 3.7.      Repayment to the Company.....................................................     29
    Section 3.8.      No Sinking Fund..............................................................     29

ARTICLE IV PURCHASE AT THE OPTION OF HOLDERS ON SPECIFIC DATES.....................................     29
    Section 4.1.      Optional Put.................................................................     29
    Section 4.2.      Effect of Purchase Notice; Withdrawal of Purchase Notice.....................     34
    Section 4.3.      Deposit of Purchase Price....................................................     34
    Section 4.4.      Certificated Securities Purchased in Part....................................     35
    Section 4.5.      Covenant to Comply With Securities Laws Upon Purchase of Securities..........     35
    Section 4.6.      Repayment to the Company.....................................................     35
    Section 4.7.      No Purchase Upon Event of Default............................................     35
</TABLE>

                                       i
<PAGE>

<TABLE>
<S>                                                                                                     <C>
ARTICLE V PURCHASE AT THE OPTION OF HOLDERS UPON A FUNDAMENTAL CHANGE..............................     36
    Section 5.1.      Fundamental Change Put.......................................................     36
    Section 5.2.      Effect of Fundamental Change Purchase Notice.................................     39
    Section 5.3.      Deposit of Fundamental Change Purchase Price.................................     39
    Section 5.4.      Certificated Securities Purchased in Part....................................     40
    Section 5.5.      Covenant to Comply With Securities Laws Upon Purchase of Notes...............     40
    Section 5.6.      Repayment to the Company.....................................................     40

ARTICLE VI COVENANTS...............................................................................     41
    Section 6.1.      Payment of Notes.............................................................     41
    Section 6.2.      SEC and Other Reports to the Trustee.........................................     42
    Section 6.3.      Compliance Certificate.......................................................     42
    Section 6.4.      Further Instruments and Acts.................................................     43
    Section 6.5.      Maintenance of Office or Agency of the Trustee, Registrar, Paying
                         Agent and Conversion Agent................................................     43
    Section 6.6.      Delivery of Information Required Under Rule 144A.............................     43
    Section 6.7.      Waiver of Stay, Extension or Usury Laws......................................     43
    Section 6.8.      Statement by Officers as to Default..........................................     44
    Section 6.9.      Payment of Additional Amounts................................................     44
    Section 6.10.     Indemnification for Foreign Currency Judgments...............................     46

ARTICLE VII SUCCESSOR CORPORATION..................................................................     46
    Section 7.1.      When Company May Merge or Transfer Assets....................................     46

ARTICLE VIII DEFAULTS AND REMEDIES.................................................................     47
    Section 8.1.      Events of Default............................................................     47
    Section 8.2.      Acceleration.................................................................     49
    Section 8.3.      Other Remedies...............................................................     49
    Section 8.4.      Waiver of Past Defaults......................................................     50
    Section 8.5.      Control by Majority..........................................................     50
    Section 8.6.      Limitation on Suits..........................................................     50
    Section 8.7.      Rights of Holders to Receive Payment or to Convert...........................     51
    Section 8.8.      Collection Suit by Trustee...................................................     51
    Section 8.9.      Trustee May File Proofs of Claim.............................................     51
    Section 8.10.     Priorities...................................................................     52
    Section 8.11.     Undertaking for Costs........................................................     52

ARTICLE IX TRUSTEE.................................................................................     53
    Section 9.1.      Duties of Trustee............................................................     53
    Section 9.2.      Rights of Trustee............................................................     54
    Section 9.3.      Individual Rights of Trustee.................................................     55
    Section 9.4.      Trustee's Disclaimer.........................................................     56
    Section 9.5.      Notice of Defaults...........................................................     56
    Section 9.6.      Reports by Trustee to Holders................................................     56
    Section 9.7.      Compensation and Indemnity...................................................     56
    Section 9.8.      Replacement of Trustee.......................................................     57
</TABLE>

                                       ii
<PAGE>

<TABLE>
<S>                                                                                                     <C>
    Section 9.9.      Successor Trustee by Merger..................................................     58
    Section 9.10.     Eligibility; Disqualification................................................     58
    Section 9.11.     Preferential Collection of Claims Against Company............................     59

ARTICLE X DISCHARGE OF INDENTURE...................................................................     59
    Section 10.1.     Discharge of Liability on Securities.........................................     59
    Section 10.2.     Repayment to the Company.....................................................     59

ARTICLE XI AMENDMENTS..............................................................................     59
    Section 11.1.     Without Consent of Holders of Notes..........................................     59
    Section 11.2.     With Consent of Holders of Notes.............................................     60
    Section 11.3.     Compliance with Trust Indenture Act..........................................     62
    Section 11.4.     Revocation and Effect of Consents, Waivers and Actions.......................     62
    Section 11.5.     Notation on or Exchange of Securities........................................     62
    Section 11.6.     Trustee to Sign Supplemental Indentures......................................     62
    Section 11.7.     Effect of Supplemental Indentures............................................     62

ARTICLE XII CONVERSION.............................................................................     63
    Section 12.1.     Conversion Right.............................................................     63
    Section 12.2.     Conversion Procedures; Conversion Rate; Fractional Shares....................     65
    Section 12.3.     Adjustment of Conversion Rate................................................     67
    Section 12.4.     Consolidation or Merger of the Company.......................................     75
    Section 12.5.     Notice of Adjustment.........................................................     77
    Section 12.6.     Notice in Certain Events.....................................................     77
    Section 12.7.     Company to Reserve Stock: Registration; Listing..............................     78
    Section 12.8.     Taxes on Conversion..........................................................     79
    Section 12.9.     Conversion After Regular Record Date.........................................     79
    Section 12.10.    Company Determination Final..................................................     79
    Section 12.11.    Responsibility of Trustee for Conversion Provisions..........................     80
    Section 12.12.    Unconditional Right of Holders to Convert....................................     80
    Section 12.13.    Option to Satisfy Conversion Obligation with Cash, Common Stock or
                        Combination Thereof........................................................     80

ARTICLE XIII MISCELLANEOUS.........................................................................     82
    Section 13.1.     Trust Indenture Act Controls.................................................     82
    Section 13.2.     Notices......................................................................     82
    Section 13.3.     Communication by Holders with Other Holders..................................     83
    Section 13.4.     Certificate and Opinion as to Conditions Precedent...........................     83
    Section 13.5.     Statements Required in Certificate or Opinion................................     84
    Section 13.6.     Separability Clause..........................................................     84
    Section 13.7.     Rules by Trustee, Paying Agent, Conversion Agent, Registrar..................     84
    Section 13.8.     Legal Holidays...............................................................     84
    Section 13.9.     Governing Law; Submission to Jurisdiction; Service of Process................     85
    Section 13.10.    No Recourse Against Others...................................................     85
    Section 13.11.    Successors...................................................................     86
    Section 13.12.    Multiple Originals...........................................................     86
    Section 13.13.    Table of Contents, Headings, Etc.............................................     86
</TABLE>

                                      iii
<PAGE>

EXHIBIT A    Form of Security

EXHIBIT B    Form of Certificate to be Delivered by Transferee in Connection
             with Transfers to Institutional Accredited Investors

EXHIBIT C    Form of Restrictive Legend for Common Stock Issues Upon Conversion

                                       iv
<PAGE>

            THIS INDENTURE, dated as of March 12, 2004, is between Willbros
Group, Inc., a Panamanian corporation (the "COMPANY"), and JPMorgan Chase Bank,
a New York banking corporation, as Trustee (the "TRUSTEE").

                            RECITALS OF THE COMPANY

            The Company has duly authorized the creation of an issue of its
2.75% Convertible Senior Notes due 2024 (the "NOTES") having the terms, tenor,
amount and other provisions hereinafter set forth, and, to provide therefor, the
Company has duly authorized the execution and delivery of this Indenture.

            All things necessary to make the Securities, when the Securities are
duly issued and executed by the Company and duly authenticated and delivered
hereunder, the valid obligations of the Company, and to make this Indenture a
valid and binding agreement of the Company, in accordance with their and its
terms, have been done.

                   NOW, THEREFORE, THIS INDENTURE WITNESSETH:

            Each party agrees as follows for the benefit of the other party and
for the equal and ratable benefit of the Holders of the Securities:

                                   ARTICLE I

                   DEFINITIONS AND INCORPORATION BY REFERENCE

      Section 1.1. Definitions.

            "ADDITIONAL AMOUNTS" has the meaning set forth in Section 6.9.

            "ADDITIONAL INTEREST" has the meaning set forth in the Registration
Rights Agreement.

            "ADDITIONAL SHARES" has the meaning set forth in the Registration
Rights Agreement.

            "AFFILIATE" of any specified person means any other person directly
or indirectly controlling or controlled by or under direct or indirect common
control with such specified person. For the purposes of this definition,
"control" when used with respect to any specified person means the power to
direct or cause the direction of the management and policies of such person,
directly or indirectly, whether through the ownership of voting securities, by
contract or otherwise; and the terms "controlling" and "controlled" have
meanings correlative to the foregoing.

            "AGENT MEMBERS" has the meaning set forth in Section 2.1(c).

            "AGREEMENT CURRENCY" has the meaning set forth in Section 6.10.

<PAGE>

            "APPLICABLE PROCEDURES" means, with respect to any transfer or
transaction involving a Global Security or beneficial interest therein, the
rules and procedures of the Depositary for such Security, in each case to the
extent applicable to such transaction and as in effect from time to time.

            "APPLICABLE STOCK" means (a) the Common Stock and/or (b) in the
event of a transaction referred to in Section 12.4 in which the Securities
become convertible into Equity Interests of another Person, such Equity
Interests or any other Equity Interests into which such Equity Interests shall
be reclassified or changed.

            "BANKRUPTCY LAW" means Title 11, United States Code, or any similar
United States federal or state law or any similar foreign law for the relief of
debtors.

            "BOARD OF DIRECTORS" means either the board of directors of the
Company or any duly authorized committee of such board.

            "BOARD RESOLUTION" means a resolution of the Board of Directors.

            "BUSINESS DAY" means each day of the year other than a Saturday or a
Sunday or other day on which banking institutions in the City of New York are
required or authorized by law, regulation or executive order to close.

            The term "CASH" means such coin or currency of the United States as
at any time of payment is legal tender for the payment of public and private
debts.

            "CASH AMOUNT" has the meaning set forth in Section 12.13(a).

            "CASH SETTLEMENT AVERAGING PERIOD" has the meaning set forth in
Section 12.13(a).

            "CERTIFICATED NOTES" or "CERTIFICATED SECURITIES" means Securities
that are in substantially the form attached hereto as Exhibit A and that do not
include the information called for by footnote 1 thereof.

            "CLOSING SALE PRICE" means with respect to a share of Applicable
Stock on any date, the closing sale price of a share of Applicable Stock (or, if
no closing sale price is reported, the average of the bid and ask prices or, if
there is more than one bid or ask price, the average of the average bid and the
average ask prices) on such date as reported on a national securities exchange
or, if the shares of Applicable Stock are not listed for trading on a national
securities exchange, as reported by the Nasdaq National Market. If the
Applicable Stock is not listed for trading on a national securities exchange and
not quoted by the Nasdaq National Market on the relevant date, the "Closing Sale
Price" shall be the last quoted bid for the Applicable Stock in the
over-the-counter market on the relevant date as reported by the National
Quotation Bureau or similar organization. If the Applicable Stock is not so
quoted, the "Closing Sale Price" shall be the average of the midpoint of the
last bid and ask prices for the Applicable Stock on the relevant date from each
of at least three nationally recognized independent investment banking firms
selected by the Company for this purpose.

                                       2
<PAGE>

            "CODE" means the Internal Revenue Code of 1986, as amended.

            "COMMON STOCK" means the common stock, $0.05 par value per share, of
the Company as that stock exists on the date of this Indenture or any other
Equity Interests of the Company into which such Common Stock shall be
reclassified or changed; provided, that after the consummation of any
transaction referred to in Section 12.4, all references to "Common Stock" shall,
to the extent necessary to protect the interests of the Holders of the
Securities, become references to "Applicable Stock."

            "COMPANY REQUEST" or "COMPANY ORDER" means a written request or
order signed in the name of the Company by any two Officers, at least one of
whom is the Chief Executive Officer or the Chief Financial Officer.

            "COMPANY" means the party named as the "Company" in the first
paragraph of this Indenture until a successor replaces it pursuant to the
applicable provisions of this Indenture and, thereafter, means such successor.
The foregoing sentence shall likewise apply to any subsequent successor or
successors to such successors.

            "COMPANY NOTICE" has the meaning set forth in Section 4.1(b).

            "CONVERSION AGENT" has the meaning set forth in Section 2.3.

            "CONVERSION NOTICE" has the meaning set forth in Section 12.2(b).

            "CONVERSION OBLIGATION" has the meaning set forth in Section
12.13(a).

            "CONVERSION PERIOD" means the period from and including the
mid-point date in a fiscal quarter of the Company to, but not including, the
mid-point date (or, if that day is not a Trading Day, then the next Trading Day)
in the immediately following fiscal quarter of the Company. The "mid-point
dates" for each of the Company's fiscal quarters are February 15, May 15, August
15 and November 15 and, for purposes of determining Conversion Periods
hereunder, such mid-point dates shall not change notwithstanding any change in
the Company's fiscal periods.

            "CONVERSION PRICE" means, at any time, $1,000 divided by the
Conversion Rate in effect at such time, rounded to two decimal places (rounded
up if the third decimal place thereof is 5 or more and otherwise rounded down).

            "CONVERSION RATE" means the number of shares of Common Stock
issuable upon conversion of each $1,000 of principal amount of Notes, which is
initially 51.3611 shares, subject to adjustments as set forth in this Indenture.

            "CORPORATE TRUST OFFICE" means the principal office of the Trustee
in the Borough of Manhattan, New York City, at which at any time its corporate
trust business shall be administered, which office at the date hereof is located
at 4 New York Plaza, Floor 15, New York, New York, 10004, or such other address
in the Borough of Manhattan, New York City, as the Trustee may designate from
time to time by notice to the Holders and the Company, or the principal
corporate trust office in the Borough of Manhattan, New York City, of any
successor

                                       3
<PAGE>

Trustee (or such other address as a successor Trustee may designate from time to
time by notice to the Holders and the Company).

            "CURRENT MARKET PRICE" has the meaning set forth in Section 12.3(g).

            "CUSTODIAN" means any receiver, trustee, assignee, liquidator,
custodian or similar official under any Bankruptcy Law.

            "DEFAULT" means, when used with respect to the Notes, any event
which is, or after notice or passage of time or both would be, an Event of
Default.

            "DEPOSITARY" means, with respect to any Global Securities, a
securities clearing agency that is registered as such under the Exchange Act and
is designated by the Company to act as Depositary for such Global Securities (or
any successor securities clearing agency so registered), which shall initially
be DTC.

            The term "DISTRIBUTED ASSETS" has the meaning set forth in Section
12.3(d)(A).

            "DTC" means The Depository Trust Company, a New York corporation.

            "EQUITY INTEREST" of any Person means any and all shares, interests,
rights to purchase, warrants, options, participations or other equivalents of or
interests in (however designated) corporate stock or other equity
participations, including partnership interests, whether general or limited, of
such Person.

            "EVENT OF DEFAULT" has the meaning set forth in Section 8.1.

            "EXCHANGE ACT" means the United States Securities Exchange Act of
1934, as amended or any successor statute thereto.

            "EXCESS AMOUNT" means, with respect to each $1,000 of principal
amount of a Security, as of any conversion date, a dollar amount equal to the
excess of (a) the product of (i) the Conversion Rate at such time multiplied by
(ii) the Closing Sale Price on the last Trading Day prior to such conversion
date over (b) $1,000, if any.

            "EXCESS AMOUNT CONVERSION OBLIGATION" has the meaning set forth in
Section 12.13(a).

            "EXCLUDED HOLDER" has the meaning set forth in Section 6.9.

            "EX-DIVIDEND TIME" means, with respect to any issuance or
distribution on Common Stock, the first Trading Day on which the Common Stock
trades regular way on the principal securities market on which the Common Stock
is then traded without the right to receive such issuance or distribution.

            "EXPIRATION TIME" has the meaning set forth in Section 12.3(f).

            "FAIR MARKET VALUE" has the meaning set forth in Section 12.3(g).

                                       4
<PAGE>

            "FINAL NOTICE DATE" has the meaning set forth in Section 12.13(a).

            "FIVE-TRADING-DAY MEASUREMENT PERIOD" means the five Trading Days
ending on the second Trading Day immediately preceding the first day of the
applicable Additional Amounts Period."

            "FUNDAMENTAL CHANGE" means the occurrence of any of the following
events: (i) any "person" or "group" (as such terms are used in Sections 13(d)
and 14(d) of the Exchange Act), is or becomes the "beneficial owner" (as defined
in Rules 13d-3 and 13d-5 under the Exchange Act, except that a Person shall be
deemed to have beneficial ownership of all shares that such Person has the right
to acquire, whether such right is exercisable immediately or only after the
passage of time), directly or indirectly, of more than 50% of the total
outstanding Voting Stock of the Company; (ii) during any period of two
consecutive years, individuals who at the beginning of such period constituted
the Board of Directors (together with any new directors whose election to such
Board of Directors or whose nomination for election by the stockholders of the
Company was approved by a vote of at least 66-2/3% of the directors then still
in office who were either directors at the beginning of such period or whose
election or nomination for election was previously so approved) cease for any
reason to constitute a majority of such Board of Directors then in office; (iii)
the Company consolidates with or merges with or into any Person or conveys,
transfers, sells or otherwise disposes of or leases all or substantially all of
its properties and assets to any Person, or any corporation consolidates with or
merges into or with the Company, in any such event pursuant to a transaction in
which the outstanding Voting Stock of the Company is changed into or exchanged
for cash, securities or other property, other than any such transaction where
the outstanding Voting Stock of the Company is not changed or exchanged at all
(except to the extent necessary to reflect a change in the jurisdiction of
incorporation of the Company), or where (A) the outstanding Voting Stock of the
Company is changed into or exchanged for cash, securities and other property
(other than Equity Interests of the surviving corporation) and (B) the
stockholders of the Company immediately before such transaction own, directly or
indirectly, immediately following such transaction, more than 50% of the total
outstanding Voting Stock of the surviving corporation; (iv) the Company is
liquidated or dissolved or adopts a plan of liquidation or dissolution other
than in a transaction which complies with the provisions described under ARTICLE
VII; or (v) the Notes are no longer convertible into Applicable Stock that is
listed on the New York Stock Exchange or another established national securities
exchange or traded on an established automated over-the-counter trading market
in the United States.

            A Fundamental Change shall not be deemed to have occurred if either:

                  (1)   the Closing Sale Price of the Common Stock for each of
      at least five Trading Days within:

                  (i)   the period of the ten consecutive Trading Days
            immediately after the later of the Fundamental Change or the public
            announcement of the Fundamental Change, in the case of a Fundamental
            Change resulting solely from a Fundamental Change in clause (i) of
            the definition of Fundamental Change; or

                                       5
<PAGE>

                  (ii)  the period of the ten consecutive Trading Days
            immediately preceding the Fundamental Change, in the case of a
            Fundamental Change resulting from a Fundamental Change in clauses
            (ii), (iii) or (iv) of the definition of Fundamental Change;

      is at least equal to 105% of the quotient where the numerator is the
      principal amount of a Security and the denominator is the Conversion Rate
      in effect on each of such five Trading Days, with such calculation being
      made for each Trading Day; or

                  (2)   in the case of a merger or consolidation described in
      clause (iii) of the definition of Fundamental Change, at least 95% of the
      consideration, excluding cash payments for fractional shares and cash
      payments pursuant to dissenters' approval rights, in the merger or
      consolidation constituting the Fundamental Change, consists of common
      stock traded on a U.S. national securities exchange or quoted on the
      Nasdaq National Market (or which shall be so traded or quoted when issued
      or exchanged in connection with such Fundamental Change) and as a result
      of such transaction or transactions the Notes become convertible solely
      into such common stock, excluding cash payments for fractional shares.

            "FUNDAMENTAL CHANGE PURCHASE DATE" has the meaning set forth in
Section 5.1(a).

            "FUNDAMENTAL CHANGE PURCHASE NOTICE" has the meaning set forth in
Section 5.1(c).

            "FUNDAMENTAL CHANGE PURCHASE PRICE" has the meaning set forth in
Section 5.1(a).

            "GLOBAL SECURITIES" means Securities that are in substantially the
form attached hereto as Exhibit A and that include the information called for by
footnotes 1 and 3 thereof and that are deposited with the Depositary or its
custodian and registered in the name of, the Depositary or its nominee.

            "HOLDER" means a person in whose name a Security, including any
Global Security, is registered on the Registrar's books.

            "INDEBTEDNESS" means, with respect to any person,

                  (a)   all obligations, contingent or otherwise, of such person
      (i) for borrowed money (whether or not the recourse of the lender is to
      the whole of the assets of such person or only to a portion thereof), (ii)
      evidenced by a note, debenture, bond or written instrument (including a
      purchase money obligation), (iii) in respect of leases of such person
      required, in conformity with United States generally accepted accounting
      principles, to be accounted for as capitalized lease obligations on the
      balance sheet of such person; or (iv) in respect of letters of credit
      (including reimbursement obligations with respect thereto), local
      guarantees or bankers' acceptances;

                                       6
<PAGE>

                  (b)   all obligations secured by a mortgage, pledge, lien,
      encumbrance, charge or adverse claim affecting title or resulting in an
      encumbrance to which the property or assets of such person are subject and
      as are reflected as debt on the balance sheet of such person, whether or
      not the obligations secured thereby shall have been assumed by or shall
      otherwise be such person's legal liability;

                  (c)   all obligations of such person under interest rate and
      currency swap agreements, cap, floor and collar agreements, spot and
      forward contracts and similar agreements and arrangements; and

                  (d)   all obligations of others of the type described in
      clause (a), (b) or (c) above assumed by or guaranteed in any manner by
      such person or in effect guaranteed by such person through an agreement to
      purchase, contingent or otherwise (and the obligations of such person
      under any such assumptions, guarantees or other such arrangements).

            "INDENTURE" means this Indenture, as amended or supplemented from
time to time in accordance with the terms hereof, including the provisions of
the TIA that are explicitly incorporated in this Indenture by reference to the
TIA.

            "INSTITUTIONAL ACCREDITED INVESTOR" means an institutional investor
that is an "accredited investor" as defined in Rule 501(a)(1), (2), (3) or (7)
under the Securities Act.

            "INTEREST PAYMENT DATE" has the meaning set forth in Exhibit A
attached hereto.

            "ISSUE DATE" means the first date on which the Notes are issued
under this Indenture.

            "JUDGMENT CURRENCY" has the meaning set forth in Section 6.10.

            "LEGAL HOLIDAY" means any day other than a Business Day.

            "MARKET PRICE" means, as of any Purchase Date, the average of the
Closing Sale Prices of the Applicable Stock for the five Trading Day period
ending on the third Business Day prior to the applicable Purchase Date (if the
third Business Day prior to the applicable Purchase Date is a Trading Day or, if
it is not a Trading Day, then on the last Trading Day prior to such third
Business Day), appropriately adjusted to take into account the occurrence,
during the period commencing on the first of such Trading Days during such
period and ending on such Purchase Date, of any event that would result in an
adjustment to the Conversion Rate pursuant to Section 12.3 hereof.

            "NON-ELECTING SHARE" has the meaning set forth Section 12.4.

            "NOTE PRICE" means on any date of determination the average of the
secondary market bid quotations per $1,000 principal amount of Notes obtained by
the Company for $5,000,000 principal amount of the Notes at approximately 4:00
p.m., New York City time, on such determination date from three independent
nationally recognized securities dealers the Company selects, provided that if
at least three such bids cannot reasonably be obtained by the

                                       7
<PAGE>

Company, but two such bids are obtained, then the average of the two bids shall
be used, and if only one such bid can reasonably be obtained by the Company,
this one bid shall be used. If the Company cannot reasonably obtain at least one
bid for $5,000,000 principal amount of the Notes from a nationally recognized
securities dealer or if, in the Company's reasonable judgment, the bid
quotations are not indicative of the secondary market value of the Notes, then
the "Note Price" will equal (a) the then-applicable Conversion Rate of the Notes
multiplied by (b) the Closing Sale Price of the Common Stock on such
determination date.

            "NOTES" has the meaning set forth in the Recitals of this Indenture.

            "OFFICER" means the Chief Executive Officer, the President, the
Chief Financial Officer, any Vice President, the Treasurer, or the Secretary of
the Company.

            "OFFICERS' CERTIFICATE" means a written certificate containing the
information specified in Section 13.4 and Section 13.5, signed in the name of
the Company by any two Officers, and delivered to the Trustee. An Officers'
Certificate given pursuant to Section 6.3 shall be signed by the principal
executive officer, principal financial officer or the principal accounting
officer of the Company.

            "OPINION OF COUNSEL" means a written opinion containing the
information specified in Section 13.4 and Section 13.5, from legal counsel. The
counsel may be an employee of, or counsel to, the Company.

            "PAYING AGENT" has the meaning set forth in Section 2.3.

            "PERSON" or "PERSON" means any individual, corporation, limited
liability company, partnership, joint venture, association, joint-stock company,
trust, unincorporated organization, or government or any agency or political
subdivision thereof (and for purposes of the definition of "Fundamental Change"
shall also have the meaning set forth in such definition).

            "PRINCIPAL CONVERSION SETTLEMENT ELECTION" has the meaning set forth
in Section 12.2(a).

            "PUBLIC NOTICE" by the Company shall mean publication of a notice in
a newspaper of general circulation in the City of New York or through such other
public medium as the Company may use at that time and publication of such
information on the Company's corporate website.

            "PURCHASE DATE" has the meaning set forth in Section 4.1(a).

            "PURCHASE NOTICE" has the meaning set forth in Section 4.1(c).

            "PURCHASE PRICE" has the meaning set forth in Section 4.1(a).

            "QIB" means a "qualified institutional buyer" as defined in Rule
144A.

            "RECORD DATE" has the meaning set forth in Section 12.3(g).

                                       8
<PAGE>

            "REDEMPTION DATE" means, when used with respect to any Security to
be redeemed, the date fixed for redemption pursuant to this Indenture.

            "REDEMPTION PRICE" means when used with respect to any Note to be
redeemed pursuant to any provision in this Indenture, the price at which it is
to be redeemed pursuant to this Indenture and the Notes.

            "REFERENCE PERIOD" has the meaning set forth in Section 12.3(d)(B).

            "REGISTRAR" has the meaning set forth in Section 2.3.

            "REGISTER" has the meaning set forth in Section 2.3.

            "REGISTRATION DEFAULT PERIOD" has the meaning set forth in the
Registration Rights Agreement.

            "REGISTRATION RIGHTS AGREEMENT" means the Registration Rights
Agreement, dated March 12, 2004, among the Company, Bear, Stearns & Co. Inc.,
CIBC World Markets Corp. and Credit Lyonnais Securities (USA), Inc., as amended
or supplemented from time to time.

            "REGULAR RECORD DATE" has the meaning set forth in Exhibit A
attached hereto.

            "RESPONSIBLE OFFICER" means, when used with respect to the Trustee,
the officer within the corporate trust department of the Trustee having direct
responsibility for the administration of this Indenture.

            "RESTRICTED CERTIFICATED SECURITY" means a Certificated Security
which is a Transfer Restricted Security.

            "RESTRICTED GLOBAL SECURITY" means a Global Security that is a
Transfer Restricted Security.

            "RESTRICTED SECURITY" means a Restricted Certificated Security or a
Restricted Global Security.

            "RULE 144A" means Rule 144A under the Securities Act (or any
successor provision), as it may be amended from time to time.

            "SEC" means the United States Securities and Exchange Commission, or
any successor thereto.

            "SECURITIES" means the Notes.

            "SECURITIES ACT" means the United States Securities Act of 1933, as
amended, or any successor statute thereto.

            "SETTLEMENT NOTICE PERIOD" has the meaning set forth in Section
12.13(a).

                                       9
<PAGE>

            "SHELF REGISTRATION STATEMENT" means any registration statement to
be filed by the Company covering resales by Holders of the Securities and the
Common Stock issuable upon conversion of the Notes, as specified in the
Registration Rights Agreement.

            "SIGNIFICANT SUBSIDIARY" means any existing or future, direct or
indirect, Subsidiary of the Company that would constitute a "significant
subsidiary" as such term is defined under Rule 1.02 of Regulation S-X.

            "SPECIAL RECORD DATE" has the meaning set forth in Exhibit A
attached hereto.

            "SPIN-OFF" has the meaning set forth in Section 12.3(d)(C).

            "STATED MATURITY", when used with respect to any Note, means March
15, 2024.

            "STOCKHOLDER RIGHTS PLAN" has the meaning set forth in Section
12.3(f).

            "SUBSIDIARY" means any person of which at least a majority of the
outstanding Voting Stock shall at the time directly or indirectly be owned or
controlled by the Company or by one or more Subsidiaries or by the Company and
one or more Subsidiaries.

            "SURRENDERED SECURITY" has the meaning set forth in Section 12.2(a).

            "TAXES" means any tax, duty, levy, impost, assessment or other
governmental charge of whatever nature imposed or levied by or on behalf of the
Government of Panama or by an authority or agency therein or thereof having the
power to tax, including any interest, penalties or other charges in respect
thereof.

            "TERRITORY" has the meaning set forth in Section 6.9.

            "TIA" means the United States Trust Indenture Act of 1939 as in
effect on the date of this Indenture, provided, however, that in the event the
TIA is amended after such date, TIA means, to the extent required by any such
amendment, the TIA as so amended.

            "TRADING DAY" means a day during which trading in securities
generally occurs on the principal U.S. national or regional securities exchange
on which the Applicable Stock is then listed for trading or, if the Applicable
Stock is not listed on a U.S. national or regional securities exchange, on the
Nasdaq National Market system or, if the Applicable Stock is not listed for
trading on a U.S. national or regional securities exchange and not quoted on the
Nasdaq National Market system, on the principal other market on which the
Applicable Stock is then traded (provided that no day on which trading of the
Applicable Stock is suspended on such exchange or other trading market will
count as a Trading Day) (it being understood that for purposes of this
definition a market shall include obtaining quotations or prices as provided in
the last two sentences of the definition of "Closing Sale Price," if
applicable).

            "TRANSFER CERTIFICATE" has the meaning set forth in Section 2.12(e).

            "TRANSFER RESTRICTED SECURITY" has the meaning set forth in Section
2.12(e).

                                       10
<PAGE>

            "TRIGGER EVENT" has the meaning set forth in Section 12.3(d)(D).

            "TRUSTEE" means the party named as the "Trustee" in the first
paragraph of this Indenture until a successor replaces it pursuant to the
applicable provisions of this Indenture and, thereafter, shall mean such
successor. The foregoing sentence shall likewise apply to any subsequent such
successor or successors.

            "UNDISRUPTED TRADING DAY" means a Trading Day on which the
Applicable Stock does not experience any of the following at any time during the
one-hour period ending at the conclusion of the regular Trading Day:

                  (a)   any suspension of or limitation imposed on trading of
      the Applicable Stock on any national or regional securities exchange or
      association or over-the-counter market;

                  (b)   any event (other than an event listed in clause (c)
      below) that disrupts or impairs the ability of market participants in
      general to (i) effect transactions in or obtain market values for the
      Applicable Stock on any relevant national or regional securities exchange
      or association or over-the-counter market or (ii) effect transactions in
      or obtain market values for, futures or options contracts relating to the
      Applicable Stock on any relevant national or regional securities exchange
      or association or over-the-counter market; or

                  (c)   any relevant national or regional securities exchange or
      association or over-the-counter market on which the Applicable Stock
      trades closes on any exchange Trading Day prior to its scheduled closing
      time unless such earlier closing time is announced by the exchange at
      least one hour prior to the earlier of (i) the actual closing time for the
      regular trading session on such exchange and (ii) the submission deadline
      for orders to be entered into the exchange for execution on such Trading
      Day,

if, in the case of clauses (a) and (b) (but not clause (c)) above, the Company
determines the effect of such suspension, limitation, disruption or impairment
is material.

            "UNRESTRICTED CERTIFICATED SECURITY" means a Certificated Security
that is not a Transfer Restricted Security.

            "UNRESTRICTED GLOBAL SECURITY" means a Global Security that is not a
Transfer Restricted Security.

            "VOTING STOCK" of a person means the Equity Interest of such person
of the class or classes pursuant to which the holders thereof have the general
voting power under ordinary circumstances to elect at least a majority of the
board of directors, managers or trustees of such person (irrespective of whether
or not at the time the Equity Interest of any other class or classes shall have
or might have voting power by reason of the happening of any contingency).

            "WITHHOLDING TAX REDEMPTION" has the meaning set forth in Section
3.1.

                                       11
<PAGE>

      Section 1.2. Incorporation by Reference of Trust Indenture Act.

            Whenever this Indenture refers to a provision of the TIA, the
provision is incorporated by reference in and made a part of this Indenture. The
following TIA terms used in this Indenture have the following meanings:

            "INDENTURE SECURITIES" means the Securities;

            "INDENTURE SECURITY HOLDER" means a Holder;

            "INDENTURE TO BE QUALIFIED" means this Indenture;

            "INDENTURE TRUSTEE" or "institutional trustee" means the Trustee;
and

            "OBLIGOR" on the indenture securities means the Company.

            All other TIA terms used but not defined in this Indenture that are
defined by the TIA, defined by TIA reference to another statute or defined by
SEC rule have the meanings assigned to them by such definitions.

      Section 1.3. Rules of Construction.

            Unless the context otherwise requires:

            (a) a term has the meaning assigned to it;

            (b) an accounting term not otherwise defined has the meaning
assigned to it in accordance with accounting principles generally accepted in
the United States as in effect from time to time;

            (c) "or" is not exclusive;

            (d) "including" means including, without limitation; and

            (e) words in the singular include the plural, and words in the
plural include the singular; and

            (f) all references to "days" mean calendar days and not Business
Days.

      Section 1.4. Acts of Holders.

            (a) Whenever in this Indenture it is provided that the Holders of a
specified percentage in aggregate principal amount of the Securities may take
action (including the making of any demand or request, the giving of any
direction, notice, consent or waiver or the taking of any other action) the fact
that at the time of taking any such action the Holders of such specified
percentage have joined therein may be evidenced (a) by any instrument or any
number of instruments of similar tenor executed by Holders in Person or by agent
or proxy appointed in writing, (b) by the record of the Holders voting in favor
thereof at any meeting of Holders duly called and held in accordance with
procedures approved by the Trustee, (c) by a combination of

                                       12
<PAGE>

such instrument or instruments and any such record of such a meeting of Holders
or (d) in the case of Securities evidenced by a Global Security, by any
electronic transmission or other message, whether or not in written format, that
complies with the Depositary's Applicable Procedures. Such evidence (and the
action embodied therein and evidenced thereby) are herein sometimes referred to
as the "ACT" of the relevant Holders. Proof of execution of any such instrument
or of a writing appointing any such agent shall be sufficient for any purpose of
this Indenture and conclusive in favor of the Trustee and the Company, if made
in the manner provided in this Section 1.4.

            (b) The fact and date of the execution by any person of any such
instrument or writing may be proved by the affidavit of a witness of such
execution or by a certificate of a notary public or other officer authorized by
law to take acknowledgments of deeds, certifying that the individual signing
such instrument or writing acknowledged to such officer the execution thereof.
Where such execution is by a signer acting in a capacity other than such
signer's individual capacity, such certificate or affidavit shall also
constitute sufficient proof of such signer's authority, if it so states. The
fact and date of the execution of any such instrument or writing, or the
authority of the person executing the same, may also be proved in any other
manner which the Trustee deems sufficient.

            (c) The principal amount and serial number of any Security and the
record ownership of Securities shall be proved by the Register maintained by the
Registrar for the Securities.

            (d) Any request, demand, authorization, direction, notice, consent,
waiver or other Act of the Holder of any Security shall bind every future Holder
of the same Security and the Holder of every Security issued upon the
registration of transfer thereof or in exchange therefor or in lieu thereof in
respect of anything done, omitted or suffered to be done by the Trustee or the
Company in reliance thereon, whether or not notation of such action is made upon
such Security.

            (e) If the Company shall solicit from the Holders any request,
demand, authorization, direction, notice, consent, waiver or other Act, the
Company may, at its option, by or pursuant to a Board Resolution, fix in advance
a record date for the determination of Holders entitled to give such request,
demand, authorization, direction, notice, consent, waiver or other Act, but the
Company shall have no obligation to do so. If such a record date is fixed, such
request, demand, authorization, direction, notice, consent, waiver or other Act
may be given before or after such record date, but only the Holders of record at
the close of business on such record date shall be deemed to be Holders for the
purposes of determining whether Holders of the requisite proportion of
outstanding Securities have authorized or agreed or consented to such request,
demand, authorization, direction, notice, consent, waiver or other Act, and for
that purpose the outstanding Securities shall be computed as of such record
date; provided that no such authorization, agreement or consent by the Holders
on such record date shall be deemed effective unless it shall become effective
pursuant to the provisions of this Indenture not later than six months after the
record date.

                                       13
<PAGE>

                                   ARTICLE II

                                 THE SECURITIES

      Section 2.1. Form and Dating.

            (a) The Notes shall be designated as the "2.75% Convertible Senior
Notes due 2024" of the Company. The aggregate principal amount of Notes
outstanding at any time may not exceed $70,000,000 except as provided in Section
2.7. The Notes shall constitute senior general obligations of the Company.

            The Securities and the Trustee's certificate of authentication shall
be substantially in the form of Exhibit A attached hereto, which is incorporated
in and made a part of this Indenture. The Securities may have notations, legends
or endorsements required by law, stock exchange rule or usage (provided that any
such notation, legend or endorsement required by usage is in a form acceptable
to the Company). The Company shall provide any such notations, legends or
endorsements to the Trustee in writing. Each Security shall be dated the date of
its authentication.

            (b) Restricted Global Securities. All of the Securities are being
initially offered and sold only to QIBs in reliance on Rule 144A and shall be
issued, initially in the form of one or more Restricted Global Securities, which
shall be deposited with the Trustee at its Corporate Trust Office, as custodian
for the Depositary and registered in the name of DTC or the nominee thereof,
duly executed by the Company and authenticated by the Trustee as hereinafter
provided. If any Securities are resold to an Institutional Accredited Investor,
the Company shall duly execute and the Trustee shall duly authenticate and
deliver, in accordance with Section 2.2, one or more additional Restricted
Global Securities, which shall be deposited with the Trustee at its Corporate
Trust Office, as custodian for the Depositary and registered in the name of DTC
or the nominee thereof and in which beneficial interests may be held by
Institutional Accredited Investors in accordance with the Applicable Procedures.
Subject to Section 2.1(a), the aggregate principal amount of the Restricted
Global Securities may from time to time be increased or decreased by adjustments
made on the records of the Trustee and the Depositary as hereinafter provided.

            (c) Global Securities in General. Each Global Security shall
represent such of the outstanding Securities as shall be specified therein and
each shall provide that it shall initially represent the aggregate amount of
outstanding Securities stated thereon, but that the aggregate amount of
outstanding Securities represented thereby may from time to time be reduced or
increased, as appropriate, to reflect exchanges, redemptions, repurchases and
conversions of such Securities.

            Any adjustment of the aggregate principal amount of a Global
Security to reflect the amount of any increase or decrease in the amount of
outstanding Securities represented thereby shall be made by the Trustee in
accordance with instructions given by the Holder thereof as required by Section
2.12 and shall be made on the records of the Trustee and the Depositary.

                                       14
<PAGE>

            Neither any members of, or participants in, the Depositary
(collectively, the "AGENT MEMBERS") nor any other persons on whose behalf Agent
Members may act may exercise any rights under this Indenture with respect to any
Global Security registered in the name of the Depositary or any nominee thereof,
or under any such Global Security, and the Depositary or such nominee, as the
case may be, may be treated by the Company, the Trustee and any agent of the
Company or the Trustee as the absolute owner and holder of such Global Security
for all purposes whatsoever. Notwithstanding the foregoing, nothing contained
herein shall (A) prevent the Company, the Trustee or any agent of the Company or
the Trustee from giving effect to any written certification, proxy or other
authorization furnished by the Depositary or such nominee, as the case may be,
or (B) impair, as between the Depositary, its Agent Members and any other person
on whose behalf an Agent Member may act, the operation of customary practices of
such Persons governing the exercise of the rights of a holder of any Security.

            (d) Certificated Securities. Certificated Securities will be issued
only under the limited circumstances provided in Section 2.12(a)(i).

      Section 2.2. Execution and Authentication.

            The Securities shall be executed on behalf of the Company by any
Officer. The signature of the Officer on the Securities may be manual or
facsimile.

            A Security bearing the manual or facsimile signature of an
individual who was at the time of the execution of the Security an Officer shall
bind the Company, notwithstanding that such individual has ceased to hold such
office(s) prior to the authentication and delivery of such Securities or did not
hold such office(s) at the date of authentication of such Securities.

            No Security shall be entitled to any benefit under this Indenture or
be valid or obligatory for any purpose unless there appears on such Security a
certificate of authentication substantially in the form provided for herein duly
executed by the Trustee by manual signature of an authorized signatory, and such
certificate upon any Security shall be conclusive evidence, and the only
evidence, that such Security has been duly authenticated and delivered
hereunder.

            The Trustee shall authenticate and deliver the Securities for
original issuance in an aggregate principal amount of up to $70,000,000 upon one
or more Company Orders without any further action by the Company. The aggregate
principal amount of the Securities outstanding at any time may not exceed
$70,000,000 except as provided in Section 2.7.

            The Trustee shall act as the initial authenticating agent.
Thereafter, the Trustee may appoint an authenticating agent acceptable to the
Company to authenticate Securities. An authenticating agent may authenticate
Securities whenever the Trustee may do so. Each reference in this Indenture to
authentication by the Trustee includes authentication by such agent.

            The Securities shall be issued only in registered form without
coupons and only in denominations of $1,000 of principal amount and any integral
multiple thereof.

                                       15
<PAGE>

      Section 2.3. Registrar, Paying Agent and Conversion Agent.

            The Company shall maintain an office or agency where Securities may
be presented for registration of transfer or for exchange ("REGISTRAR"), an
office or agency where Securities may be presented for redemption, repurchase or
payment ("PAYING AGENT"), an office or agency where Securities may be presented
for conversion ("CONVERSION AGENT") and an office or agency where notices and
demands to or upon the Company in respect of the Securities and this Indenture
may be served. The Registrar shall keep a register of the Securities (the
"REGISTER") and of their transfer and exchange.

            The Company may have one or more co-registrars, one or more
additional paying agents and one or more additional conversion agents. The term
Paying Agent includes any additional paying agent, including any named pursuant
to Section 6.5. The term Conversion Agent includes any additional conversion
agent, including any named pursuant to Section 6.5.

            The Company shall enter into an appropriate limited agency agreement
with any Registrar, Paying Agent, Conversion Agent or co-registrar (in each
case, if such Registrar, agent or co-registrar is a Person other than the
Trustee). Each such agreement shall implement the provisions of this Indenture
that relate to such agent. The Company shall notify the Trustee of the name and
address of any such agent. If the Company fails to maintain a Registrar, Paying
Agent or Conversion Agent, the Trustee shall act as such and shall be entitled
to appropriate compensation therefor pursuant to Section 9.7.

            The Company hereby initially appoints the Trustee as Registrar,
Paying Agent and Conversion Agent at its Corporate Trust Office in connection
with the Securities.

      Section 2.4. Paying Agent to Hold Assets in Trust.

            Except as otherwise provided herein, prior to 11:00 a.m., New York
City time, on each due date of cash payments in respect of any Security, the
Company shall deposit with the Paying Agent, cash (in immediately available
funds if deposited on the due date) sufficient to make such payments when so
becoming due. The Company shall require each Paying Agent (other than the
Trustee) to agree in writing that the Paying Agent shall hold in trust for the
benefit of Holders or the Trustee all cash held by the Paying Agent for the
making of payments in respect of the Securities and shall notify the Trustee of
any default by the Company in making any such payment. The Company at any time
may require a Paying Agent to pay all cash held by it to the Trustee, and to
account for any funds disbursed by it, and the Trustee may at any time during
the continuance of any such default, upon the written request to the Paying
Agent, require such Paying Agent to forthwith pay to the Trustee all cash so
held in trust. Upon doing so, the Paying Agent shall have no further liability
for the cash.

      Section 2.5. Holder Lists.

            The Trustee shall preserve in as current a form as is reasonably
practicable the most recent list available to it of the names and addresses of
Holders and shall otherwise comply with TIA Section 312(a). If the Trustee is
not the Registrar, the Company shall cause to be furnished to the Trustee on or
before each semiannual Interest Payment Date and at such other

                                       16
<PAGE>

times as the Trustee may request in writing a list in such form and as of such
date as the Trustee may reasonably require of the names and addresses of
Holders.

      Section 2.6. Transfer and Exchange.

            (a) Subject to compliance with any applicable additional
requirements contained in Section 2.12, when a Security is presented to the
Registrar with a request to register a transfer thereof or to exchange such
Security for an equal principal amount of Securities of other authorized
denominations, the Registrar shall register the transfer or make the exchange as
requested; provided, however, that every Security presented or surrendered for
registration of transfer or exchange shall be duly endorsed or accompanied by an
assignment form and, if applicable, a transfer certificate, each in the form
included in Exhibit A attached hereto and in form satisfactory to the Registrar
and each duly executed by the Holder thereof or its attorney duly authorized in
writing. To permit registration of transfers and exchanges, upon surrender of
any Security for registration of transfer or exchange at an office or agency
maintained for such purpose pursuant to Section 2.3, the Company shall execute,
and the Trustee shall authenticate, Securities of a like aggregate principal
amount at the Registrar's request. Any transfer or exchange shall be without
charge, except that the Company or the Registrar may require payment of a sum
sufficient to pay all taxes, assessments or other governmental charges that may
be imposed in connection with the transfer or exchange of the Securities from
the Holder requesting such transfer or exchange.

            Neither the Company, the Registrar nor the Trustee shall be required
to exchange or register a transfer of (i) any Securities selected for redemption
(except, in the case of Securities to be redeemed in part, the portion thereof
not to be redeemed), or (ii) any Securities in respect of which a Purchase
Notice or a Fundamental Change Purchase Notice has been given and not withdrawn
by the Holder thereof in accordance with the terms of this Indenture (except, in
the case of Securities to be repurchased in part, the portion thereof not to be
repurchased), or (iii) any Securities surrendered for conversion (except, in the
case of Securities to be converted in part, the portion thereof not to be
converted).

            All Securities issued upon any transfer or exchange of Securities
shall be valid obligations of the Company, evidencing the same debt and entitled
to the same benefits under this Indenture, as the Securities surrendered upon
such transfer or exchange.

            (b) Any Registrar appointed pursuant to Section 2.3 shall provide to
the Trustee such information as the Trustee may reasonably require in connection
with the delivery by such Registrar of Securities upon transfer or exchange of
Securities.

            (c) The Trustee shall have no obligation or duty to monitor,
determine or inquire as to compliance with any restrictions on transfer imposed
under this Indenture or under applicable law with respect to any transfer of any
interest in any Security between or among Agent Members or other beneficial
owners of interests in any Global Security other than to require delivery of
such certificates and other documentation or evidence as are expressly required
by, and to do so if and when expressly required by the terms of, this Indenture,
and to examine the same to determine substantial compliance as to form with the
express requirements hereof.

                                       17
<PAGE>

      Section 2.7. Replacement Securities.

            If (a) any mutilated Security is surrendered to the Company, the
Registrar or the Trustee, or (b) the Company, the Registrar and the Trustee
receive evidence to their satisfaction of the destruction, loss or theft of any
Security, and there is delivered to the Company, the Registrar and the Trustee
such security or indemnity as may be requested by them to save each of them
harmless, then, in the absence of any notice to the Company, the Registrar or
the Trustee that such Security has been acquired by a protected purchaser
(within the meaning of Section 8-303 of the Uniform Commercial Code as adopted
in the State of New York), the Company shall execute and upon its written
request the Trustee shall authenticate and deliver, in exchange for any such
mutilated Security or in lieu of any such destroyed, lost or stolen Security, a
new Security of like tenor and principal amount, bearing a certificate number
not contemporaneously outstanding.

            In case any such mutilated, destroyed, lost or stolen Security has
become or is about to become due and payable, or is about to be redeemed by the
Company pursuant to ARTICLE III or repurchased by the Company pursuant to
ARTICLE IV or ARTICLE V, the Company in its discretion may, instead of issuing a
new Security, pay, redeem or repurchase such Security, as the case may be.

            Upon the issuance of any new Securities under this Section 2.7, the
Company may require the payment of a sum sufficient to cover any tax, assessment
or other governmental charge that may be imposed in relation thereto and any
other expenses (including the fees and expenses of the Trustee or the Registrar)
connected therewith.

            Every new Security issued pursuant to this Section 2.7 in lieu of
any mutilated, destroyed, lost or stolen Security shall constitute an original
additional contractual obligation of the Company, whether or not the destroyed,
lost or stolen Security shall be at any time enforceable by anyone, and shall be
entitled to all benefits of this Indenture equally and proportionately with any
and all other Securities duly issued hereunder.

            The provisions of this Section 2.7 are exclusive and shall preclude
(to the extent lawful) all other rights and remedies with respect to the
replacement or payment of mutilated, destroyed, lost or stolen Securities.

      Section 2.8. Outstanding Securities; Determinations of Holders' Action.

            Securities outstanding at any time are all the Securities
authenticated by the Trustee, except for those cancelled by it, those delivered
to it for cancellation, and those described in this Section 2.8 as not
outstanding. If a Security is replaced pursuant to Section 2.7, the replaced
Security ceases to be outstanding unless the Trustee receives proof satisfactory
to it that the replaced Security is held by a protected purchaser unaware that
such Security has been replaced.

            A Security does not cease to be outstanding because the Company or
an Affiliate thereof holds the Security; provided, however, that in determining
whether the Holders of the requisite principal amount of Securities have given
or concurred in any request, demand, authorization, direction, notice, consent,
waiver, or other Act hereunder, Securities owned by the

                                       18
<PAGE>

Company or any other obligor upon the Securities or any Affiliate of the Company
or such other obligor shall be disregarded and deemed not to be outstanding,
except that, in determining whether the Trustee shall be protected in relying
upon any such request, demand, authorization, direction, notice, consent, waiver
or other Act, only Securities which a Responsible Officer of the Trustee
actually knows to be so owned shall be so disregarded; and, provided further,
that Securities that the Company or an Affiliate offers to purchase or acquires
pursuant to an offer, exchange offer, tender offer or otherwise shall not be
deemed to be owned by the Company or an Affiliate until legal title to such
Notes passes to the Company or such Affiliate, as the case may be. Subject to
the foregoing, only Securities outstanding at the time of determination shall be
considered in any such determination.

            If a Security is replaced pursuant to Section 2.7, the replaced
Security ceases to be outstanding unless the Trustee receives proof satisfactory
to it that the replaced Security is held by a bona fide purchaser unaware that
such Security has been replaced.

            If the Paying Agent holds, in accordance with the terms of this
Indenture, prior to 11:00 a.m., New York City time, on a Redemption Date, a
Purchase Date, a Fundamental Change Purchase Date or Stated Maturity, as the
case may be, cash or securities, if permitted hereunder, sufficient to pay
Securities payable on that date, then on such Redemption Date, Purchase Date,
Fundamental Change Purchase Date or Stated Maturity, as the case may be, such
Securities shall cease to be outstanding and interest, Additional Amounts and
Additional Interest, if any, on such Securities shall cease to accrue.

            If a Security is converted in accordance with ARTICLE XII, then,
from and after the time of conversion on the date of conversion, such Security
shall cease to be outstanding and interest, Additional Amounts and Additional
Interest, if any, on such Security shall cease to accrue.

      Section 2.9. Temporary Securities.

            Pending the preparation of definitive Securities, the Company may
execute, and upon Company Order, the Trustee shall authenticate and deliver,
temporary Securities which are printed, lithographed, typewritten, mimeographed
or otherwise produced, in any authorized denomination, substantially of the
tenor of the definitive Securities in lieu of which they are issued and with
such appropriate insertions, omissions, substitutions and other variations as
the Officers executing such Securities may determine, as conclusively evidenced
by their execution of such Securities.

            If temporary Securities are issued, the Company shall cause
definitive Securities to be prepared without unreasonable delay. After the
preparation of definitive Securities, the temporary Securities shall be
exchangeable for definitive Securities upon surrender of the temporary
Securities at the office or agency of the Company designated for such purpose
pursuant to Section 2.3, without charge to the Holder. Upon surrender for
cancellation of any one or more temporary Securities the Company shall execute
and the Trustee shall authenticate and deliver in exchange therefor a like
principal amount of definitive Securities of authorized denominations. Until so
exchanged the temporary Securities shall in all respects be entitled to the same
benefits and subject to the same limitations under this Indenture as definitive
Securities.

                                       19
<PAGE>

      Section 2.10. Cancellation.

            All Securities surrendered for payment, repurchase by the Company
pursuant to ARTICLE IV or ARTICLE V, conversion, redemption or registration of
transfer or exchange shall, if surrendered to any person other than the Trustee,
be delivered to the Trustee and shall be promptly cancelled by it or, if
surrendered to the Trustee, shall be promptly cancelled by it. The Company may
at any time deliver to the Trustee for cancellation any Securities previously
authenticated and delivered hereunder which the Company may have acquired in any
manner whatsoever, and all Securities so delivered shall be promptly cancelled
by the Trustee. The Company may not issue new Securities to replace Securities
that it has paid or delivered to the Trustee for cancellation or that any Holder
has converted pursuant to ARTICLE XII. No Securities shall be authenticated in
lieu of or in exchange for any Securities cancelled as provided in this Section
2.10, except as expressly permitted by this Indenture. All cancelled Securities
held by the Trustee shall be disposed of by the Trustee in accordance with the
Trustee's customary procedure.

      Section 2.11. Persons Deemed Owners.

            Prior to due presentment of a Security for registration of transfer,
the Company, the Trustee and any agent of the Company or the Trustee may treat
the person in whose name such Security is registered as the owner of such
Security for the purpose of receiving payment of principal of, Redemption Price,
Purchase Price or Fundamental Change Purchase Price, and interest, Additional
Amounts and Additional Interest, if any, on, the Security, for the purpose of
receiving cash or Applicable Stock upon conversion and for all other purposes
whatsoever, whether or not such Security be overdue, and neither the Company,
the Trustee nor any agent of the Company or the Trustee shall be affected by
notice to the contrary.

      Section 2.12. Additional Transfer and Exchange Requirements.

            (a) Transfer and Exchange of Global Securities.

            (i)   Certificated Securities shall be issued in exchange for
      interests in the Global Securities only if the Depositary notifies the
      Company that it is unwilling or unable to continue as Depositary for the
      Global Securities, the Depositary ceases to be a "clearing agency"
      registered under the Exchange Act, if so required by applicable law or
      regulation and, in either case, a successor Depositary is not appointed by
      the Company within 90 calendar days, or an Event of Default has occurred
      and is continuing and the Registrar has received a request from the
      Depositary requesting such exchange. In any such case, the Company shall
      execute, and the Trustee shall, upon receipt of a Company Order (which the
      Company agrees to deliver promptly), authenticate and deliver Certificated
      Securities in an aggregate principal amount equal to the principal amount
      of such Global Securities in exchange therefor. Only Restricted
      Certificated Securities shall be issued in exchange for beneficial
      interests in Restricted Global Securities, and only Unrestricted
      Certificated Securities shall be issued in exchange for beneficial
      interests in Unrestricted Global Securities. Certificated Securities
      issued in exchange for beneficial interests in Global Securities shall be
      registered in such names and shall be in such authorized denominations as
      the Depositary, pursuant to instructions from its direct or

                                       20
<PAGE>

      indirect participants or otherwise, shall instruct the Trustee. The
      Trustee shall deliver or cause to be delivered such Certificated
      Securities to the Persons in whose name such Securities are so registered.
      Such exchange shall be effected in accordance with the Applicable
      Procedures.

            (ii)  Notwithstanding any other provisions of this Indenture other
      than the provisions set forth in Section 2.12(a)(i), a Global Security may
      not be transferred except as a whole by the Depositary to a nominee of the
      Depositary or by a nominee of the Depositary to the Depositary or another
      nominee of the Depositary or by the Depositary or any such nominee to a
      successor Depositary or a nominee of such successor Depositary.

            (b) Transfer and Exchange of Certificated Securities. In the event
that Certificated Securities are issued in exchange for beneficial interests in
Global Securities in accordance with Section 2.12(a)(i), and, on or after such
event, Certificated Securities are presented by a Holder to the Registrar with a
request:

            (x)   to register the transfer of the Certificated Securities to a
person who will take delivery thereof in the form of Certificated Securities
only; or

            (y)   to exchange such Certificated Securities for an equal
principal amount of Certificated Securities of other authorized denominations,

such Registrar shall register the transfer or make the exchange as requested;
provided, however, that the Certificated Securities presented or surrendered for
register of transfer or exchange:

            (i)   shall be duly endorsed or accompanied by a written instrument
      of transfer in accordance with the proviso in the first paragraph of
      Section 2.6(a); and

            (ii)  in the case of a Restricted Certificated Security, such
      request shall be accompanied by the following additional information and
      documents, as applicable:

                  (A)   if such Restricted Certificated Security is being
            delivered to the Registrar by a Holder for registration in the name
            of such Holder, without transfer, or such Restricted Certificated
            Security is being transferred to the Company or a Subsidiary of the
            Company, a certification to that effect from such Holder (in
            substantially the form set forth in the Transfer Certificate);

                  (B)   if such Restricted Certificated Security is being
            transferred to a person the Holder reasonably believes is a QIB in
            compliance with Rule 144A, pursuant to the exemption from the
            registration requirements of the Securities Act provided by Rule 144
            (if available) or pursuant to an effective registration statement
            under the Securities Act, a certification to that effect from such
            Holder (in substantially the form set forth in the Transfer
            Certificate); or

                  (C)   if such Restricted Certificated Security is being
            transferred pursuant to an exemption from the registration
            requirements of the Securities Act to an Institutional Accredited
            Investor (other than to a QIB in accordance with

                                       21
<PAGE>

            Rule 144A), that, prior to such transfer, furnishes to the Trustee a
            certificate containing certain representations and warranties by
            such Institutional Accredited Investor (in substantially the form
            set forth in Exhibit B), an Opinion of Counsel if required by the
            Company or the Trustee and a certification to that effect from the
            Holder (in substantially the form set forth in the Transfer
            Certificate).

            (c) Transfer of a Beneficial Interest in a Restricted Global
Security for a Beneficial Interest in an Unrestricted Global Security. Any
person having a beneficial interest in a Restricted Global Security may upon
request, subject to the Applicable Procedures, transfer such beneficial interest
to a person who is required or permitted to take delivery thereof in the form of
an Unrestricted Global Security. Upon receipt by the Trustee of written
instructions, or such other form of instructions as is customary for the
Depositary, from the Depositary or its nominee on behalf of any person having a
beneficial interest in a Restricted Global Security and the following additional
information and documents in such form as is customary for the Depositary from
the Depositary or its nominee on behalf of the person having such beneficial
interest in the Restricted Global Security (all of which may be submitted by
facsimile or electronically):

            (i)   if such beneficial interest is being transferred pursuant to
      an effective registration statement under the Securities Act, a
      certification to that effect from the Holder (in substantially the form
      set forth in the Transfer Certificate); or

            (ii)  if such beneficial interest is being transferred pursuant to
      the exemption from the registration requirements of the Securities Act
      provided by Rule 144, a certification to that effect from the Holder (in
      substantially the form set forth in the Transfer Certificate),

the Trustee, as the Registrar, shall reduce or cause to be reduced the aggregate
principal amount of the Restricted Global Security by the appropriate principal
amount and shall increase or cause to be increased the aggregate principal
amount of the Unrestricted Global Security by a like principal amount. Such
transfer shall otherwise be effected in accordance with the Applicable
Procedures. If no Unrestricted Global Security is then outstanding, the Company
shall execute and the Trustee shall, upon receipt of a Company Order (which the
Company agrees to deliver promptly), authenticate and deliver an Unrestricted
Global Security.

            (d) Transfers of Certificated Securities for Beneficial Interests in
Global Securities. In the event that Certificated Securities are issued in
exchange for beneficial interests in Global Securities and, thereafter, the
events or conditions specified in Section 2.12(a)(i) which required such
exchange shall cease to exist, the Company shall mail notice to the Trustee and
to the Holders stating that Holders may exchange Certificated Securities for
interests in Global Securities by complying with the procedures set forth in
this Indenture and briefly describing such procedures and the events or
circumstances requiring that such notice be given. Thereafter, if Certificated
Securities are presented by a Holder to a Registrar with a request:

            (x)   to register the transfer of such Certificated Securities to a
      person who will take delivery thereof in the form of a beneficial interest
      in a Global Security, which

                                       22
<PAGE>

      request shall specify whether such Global Security will be a Restricted
      Global Security or an Unrestricted Global Security, or

            (y)   to exchange such Certificated Securities for an equal
      principal amount of beneficial interests in a Global Security, which
      beneficial interests shall be owned by the Holder transferring such
      Certificated Securities (provided that in the case of such an exchange,
      Restricted Certificated Securities may be exchanged only for beneficial
      interests in Restricted Global Securities and Unrestricted Certificated
      Securities may be exchanged only for beneficial interests in Unrestricted
      Global Securities), the Registrar shall register the transfer or make the
      exchange as requested by canceling such Certificated Security and causing,
      or directing the Registrar to cause, the aggregate principal amount of the
      applicable Global Security to be increased accordingly and, if no such
      Global Security is then outstanding, the Company shall issue and the
      Trustee shall, upon receipt of a Company Order (which the Company agrees
      to deliver promptly) authenticate and deliver a new Global Security;

provided, however, that the Certificated Securities presented or surrendered for
registration of transfer or exchange:

                        (1)   shall be duly endorsed or accompanied by a written
                  instrument of transfer in accordance with the proviso in the
                  first paragraph of Section 2.6(a);

                        (2)   in the case of a Restricted Certificated Security
                  to be transferred for a beneficial interest in an Unrestricted
                  Global Security, such request shall be accompanied by the
                  following additional information and documents, as applicable:

                        (i)   if such Restricted Certificated Security is being
                  transferred pursuant to an effective registration statement
                  under the Securities Act, a certification to that effect from
                  such Holder (in substantially the form set forth in the
                  Transfer Certificate); or

                        (ii)  if such Restricted Certificated Security is being
                  transferred pursuant to the exemption from the registration
                  requirements of the Securities Act provided by Rule 144, a
                  certification to that effect from such Holder (in
                  substantially the form set forth in the Transfer Certificate);

                        (3)   in the case of a Restricted Certificated Security
                  to be transferred or exchanged for a beneficial interest in a
                  Restricted Global Security, such request shall be accompanied
                  by a certification from such Holder (in substantially the form
                  set forth in the Transfer Certificate) to the effect that such
                  Restricted Certificated Security is being transferred to a
                  person the Holder reasonably believes is a QIB (which, in the
                  case of an exchange, shall be such Holder) in compliance with
                  Rule 144A or, in the case of a transfer to an Institutional
                  Accredited Investor (other than to a QIB in accordance with
                  Rule 144A), by a certificate containing certain

                                       23
<PAGE>

                  representations and warranties by such Institutional
                  Accredited Investor (in substantially the form set forth in
                  Exhibit B), an Opinion of Counsel if required by the Company
                  or the Trustee and a certification to that effect from the
                  Holder (in substantially the form set forth in the Transfer
                  Certificate); and

                        (4)   in the case of an Unrestricted Certificated
                  Security to be transferred or exchanged for a beneficial
                  interest in an Unrestricted Global Security, such request need
                  not be accompanied by any additional information or documents.

            (e) Legends.

                        (1)   Except as permitted by the following paragraphs
                  (2), (3) and (4), each Global Security and Certificated
                  Security (and all Securities issued in exchange therefor or
                  upon registration of transfer or replacement thereof) shall
                  bear a legend in substantially the form called for by footnote
                  2 to Exhibit A (each a "TRANSFER RESTRICTED SECURITY"), for so
                  long as it is required by this Indenture to bear such legend.
                  Each Transfer Restricted Security shall have attached thereto
                  a certificate (a "TRANSFER CERTIFICATE") in substantially the
                  form called for by footnote 4 to Exhibit A attached hereto.

                        (2)   Upon any sale or transfer of a Transfer Restricted
                  Security (x) pursuant to Rule 144 or (y) pursuant to an
                  effective registration statement under the Securities Act:

                        (i)   in the case of any Restricted Certificated
                  Security, any Registrar shall permit the Holder thereof to
                  exchange such Restricted Certificated Security for an
                  Unrestricted Certificated Security, or (under the
                  circumstances described in Section 2.12(d)) to transfer such
                  Restricted Certificated Security to a transferee who shall
                  take such Security in the form of a beneficial interest in an
                  Unrestricted Global Security, and in each case shall rescind
                  any restriction on the transfer of such Security; and

                        (ii)  in the case of any beneficial interest in a
                  Restricted Global Security, the Trustee shall permit the
                  beneficial owner thereof to transfer such beneficial interest
                  to a transferee who shall take such interest in the form of a
                  beneficial interest in an Unrestricted Global Security and
                  shall rescind any restriction on transfer of such beneficial
                  interest; provided, that such Unrestricted Global Security
                  shall continue to be subject to the provisions of Section
                  2.12(a)(ii).

                        (3)   Upon the expiration of the holding period pursuant
                  to Rule 144(k) of the Securities Act, the Company shall remove
                  any restriction of transfer on such Security, and the Company
                  shall execute, and the Trustee

                                       24
<PAGE>

                  shall authenticate and deliver Securities that do not bear
                  such legend and that do not have a Transfer Certificate
                  attached thereto.

                        (4)   Until the expiration of the holding period
                  applicable to sales of the Securities under Rule 144(k) of the
                  Securities Act or a transfer of the Securities pursuant to
                  Rule 144 or pursuant to an effective registration statement
                  under the Securities Act, the Applicable Stock issued upon
                  conversion of the Securities shall bear the legend in
                  substantially the form called for by Exhibit C attached
                  hereto.

            (f) Transfers to the Company. Nothing contained in this Indenture or
in the Securities shall prohibit the sale or other transfer of any Securities
(including beneficial interests in Global Securities) to the Company or any of
its Subsidiaries, which Securities shall thereupon be cancelled in accordance
with Section 2.10.

            (g) Amendments to Rule 144(k). Notwithstanding any other provision
in this Indenture, if Rule 144(k) as promulgated under the Securities Act is
amended to shorten the two-year period under Rule 144(k), then the references to
"two years" in the restrictive legend of each Transfer Restricted Security shall
be deemed to refer to such shorter period, from and after receipt by the Trustee
of a Company Request; provided that, such legend shall not be deemed to refer to
such shorter period if to do so would be prohibited by, or would otherwise cause
a violation of, the U.S. federal securities laws applicable at the time. As soon
as practicable after a Responsible Officer of the Company receives notice of the
effectiveness of any such amendment to shorten the two-year period under Rule
144(k), unless causing the Transfer Restricted Securities to refer to such
shorter period would otherwise be prohibited by, or would otherwise cause a
violation of, the U.S. federal securities laws applicable at the time, the
Company will provide to the Trustee a Company Request respecting the
effectiveness of such amendment.

      Section 2.13. CUSIP Numbers.

            The Company may issue the Securities with one or more "CUSIP"
numbers (if then generally in use), and, if so, the Trustee shall use "CUSIP"
numbers in notices of redemption or repurchase as a convenience to Holders;
provided that any such notice may state that no representation is made as to the
correctness of such numbers either as printed on the Securities or as contained
in any notice of a redemption or repurchase and that reliance may be placed only
on the other identification numbers printed on the Securities, and any such
redemption or repurchase shall not be affected by any defect in or omission of
such numbers. The Company shall promptly notify the Trustee of any change in the
CUSIP numbers.

                                  ARTICLE III

                              REDEMPTION OF NOTES

      Section 3.1. The Company's Right to Redeem; Notice to Trustee.

            Subject to the terms and conditions of this ARTICLE III, the Company
may, at its option, redeem for cash at any time:

                                       25
<PAGE>

            (i)   all or a portion of the Notes, beginning on March 5, 2011, at
      a Redemption Price equal to 100% of the principal amount of the Notes plus
      accrued and unpaid interest, Additional Amounts and Additional Interest,
      if any, to, but not including, the Redemption Date; and

            (ii)  the Notes in whole but not in part, at a Redemption Price of
      100% of the principal amount thereof plus accrued and unpaid interest,
      Additional Amounts and Additional Interest, if any, to, but not including,
      the Redemption Date, if the Company has become or would become obligated
      to pay any Additional Amounts in respect of the Notes as a result of
      (A)(1) any change in or amendment to the laws or treaties (or regulations
      or rulings promulgated thereunder) of the Republic of Panama or (in the
      circumstances described in the penultimate paragraph of Section 6.9
      hereof) any relevant Territory or any political subdivision or authority
      or agency thereof or therein having the power to tax or (2) any change in
      or amendment to any official position regarding the application or
      interpretation of such laws, treaties, regulations or rulings, which
      change or amendment is announced or is effective on or after the Issue
      Date and (B) such obligation cannot be avoided by the Company taking
      reasonable measures available to it. Notwithstanding the preceding
      sentence of this Section 3.1(ii), no notice of redemption of the Notes
      pursuant to this Section 3.1(ii) may be given earlier than 60 days prior
      to the earliest date on which the Company could be obligated to pay such
      Additional Amounts if a payment in respect of the Notes were then due.
      Prior to giving notice of any such redemption, the Company shall deliver
      to the Trustee (y) an Officers' Certificate stating that the obligation to
      pay Additional Amounts cannot be avoided by the Company's taking
      reasonable measures available to it and (z) an Opinion of Counsel of an
      independent legal counsel to the Company to the effect that the
      circumstances referred to in clause (A) above exist.

            Notwithstanding the foregoing, if the Company has given notice of a
redemption described in clause (ii) of this Section 3.1 (a "WITHHOLDING TAX
REDEMPTION"), each Holder shall have the right to elect that such Holder's Notes
will not be subject to such Withholding Tax Redemption. If a Holder elects not
to be subject to a Withholding Tax Redemption, the Company will not be required
to pay any Additional Amounts as provided in Section 6.9 with respect to
payments made on such Holder's Notes following the date of such Withholding Tax
Redemption, and all subsequent payments on such Holder's Notes will be subject
to any Taxes required to be withheld or deducted under Panamanian law. Holders
must exercise their option to avoid a Withholding Tax Redemption by written
notice delivered to the Trustee no later than the 15th day prior to the date of
such Withholding Tax Redemption fixed by the Company. Such notice shall identify
the Notes subject to such election and state that the Holder elects to avoid the
Withholding Tax Redemption and that the Holder will not be entitled to any
Additional Amounts with respect to payments made on such Holder's Notes
following the date of such Withholding Tax Redemption. In the case of Global
Securities, the text of such notice and the method of its delivery shall comply
with the Applicable Procedures.

            In the event that the Company elects to redeem Notes on a date that
is after any Regular Record Date but on or before the corresponding Interest
Payment Date, the Company shall be required to pay any accrued and unpaid
interest, Additional Amounts and Additional

                                       26
<PAGE>

Interest, if any, to the holder of the redeemed Note and not the Holder on the
corresponding Regular Record Date.

            If the Company elects to redeem Notes, it shall notify the Trustee
in writing of the Redemption Date, the principal amount of Notes to be redeemed
and the Redemption Price. The Company shall give this notice to the Trustee by a
Company Order at least ten Business Days before mailing the notice of redemption
pursuant to Section 3.3 (unless a shorter notice shall be satisfactory to the
Trustee).

      Section 3.2. Selection of Notes to Be Redeemed.

            If fewer than all of the outstanding Notes are to be redeemed,
unless the procedures of the Depositary provide otherwise, the Trustee shall
select the Notes to be redeemed by lot or on a pro rata basis or by another
method the Trustee considers fair and appropriate. The Trustee shall make the
selection within five Business Days after it receives the notice provided for in
Section 3.1 from outstanding Notes not previously called for redemption.

            Notes and portions of Notes that the Trustee selects shall be in
principal amounts of $1,000 or an integral multiple thereof. Provisions of this
Indenture that apply to Notes called for redemption also apply to portions of
Notes called for redemption. The Trustee shall notify the Company promptly of
the Notes or portions of the Notes to be redeemed.

            Notes and portions of Notes that are to be redeemed are convertible
by the Holder until 5:00 p.m., New York City time, on the second Business Day
immediately preceding the Redemption Date. If any Note selected for partial
redemption is converted in part before termination of the conversion right with
respect to the portion of the Note so selected, the converted portion of such
Note shall be deemed (so far as may be) to be the portion selected for
redemption. Notes which have been converted during a selection of Notes to be
redeemed may be treated by the Trustee as outstanding for the purpose of such
selection.

      Section 3.3. Notice of Redemption.

            At least 20 days but not more than 60 days before a Redemption Date,
the Company shall mail a notice of redemption by first-class mail, postage
prepaid, to each Holder of Notes to be redeemed.

            The notice of redemption shall identify the Securities to be
redeemed and shall state:

            (a) the Redemption Date;

            (b) the Redemption Price;

            (c) the Conversion Rate;

            (d) the name and address of the Paying Agent and Conversion Agent;

                                       27
<PAGE>

            (e) that Notes called for redemption may be converted at any time
prior to 5:00 p.m., New York City time, on the second Business Day preceding the
Redemption Date;

            (f) that Holders who want to convert their Notes must satisfy the
requirements set forth in ARTICLE XII;

            (g) that Notes called for redemption must be surrendered to the
Paying Agent to collect the Redemption Price;

            (h) if fewer than all of any outstanding Certificated Notes are to
be redeemed, the serial numbers, if any, and principal amounts of the particular
Notes to be redeemed;

            (i) that, unless the Company defaults in making payment of such
Redemption Price, interest, Additional Amounts and Additional Interest, if any,
on Notes called for redemption shall cease to accrue on and after the Redemption
Date;

            (j) the CUSIP number(s) of the Securities;

            (k) in the case of a Tax Withholding Redemption, the written notice
that Holders use to avoid such redemption with respect to their Notes shall be
substantially in the form supplied by the Company with such notice of redemption
and that it must be delivered to the Trustee no later than the 15th day prior to
the Redemption Date; and

            (l) any other information the Company wants to present.

            At the Company's request, the Trustee shall give the notice of
redemption in the Company's name and at the Company's expense; provided,
however, that the Company makes such request at least five Business Days (unless
a shorter period shall be satisfactory to the Trustee) prior to the date by
which such notice of redemption must be given to Holders in accordance with this
Section 3.3; provided, further, that the text of the notice of redemption shall
be prepared by the Company.

            If any of the Notes is in the form of a Global Security, then the
Company shall modify such notice to the extent necessary to accord with the
procedures of the Depositary applicable to the redemption of Global Securities.

      Section 3.4. Effect of Notice of Redemption.

            Once notice of redemption is given, Notes called for redemption
become due and payable on the Redemption Date and at the Redemption Price,
except for Notes which are converted in accordance with the terms of this
Indenture. Upon surrender to the Paying Agent, such Notes shall be paid at the
Redemption Price.

      Section 3.5. Deposit of Redemption Price.

            Prior to 11:00 a.m., New York City time, on the applicable
Redemption Date, the Company shall irrevocably deposit with the Paying Agent an
amount of cash (in immediately available funds if deposited on the Redemption
Date) sufficient to pay the aggregate Redemption

                                       28
<PAGE>

Price of all Notes or portions thereof which are to be redeemed as of such
Redemption Date other than Notes or portions of Notes called for redemption
which on or prior thereto have been delivered by the Company to the Trustee for
cancellation or have been converted.

            If the Paying Agent holds, in accordance with the terms hereof, at
11:00 a.m., New York City time, on the applicable Redemption Date, cash
sufficient to pay the Redemption Price of any Notes for which notice of
redemption is given, then, on such Redemption Date, such Notes shall cease to be
outstanding and interest, Additional Amounts and Additional Interest, if any, on
such Notes shall cease to accrue, whether or not such Notes are delivered to the
Paying Agent, and the rights of the Holders in respect thereof shall terminate
(other than the right to receive the Redemption Price upon delivery of such
Notes).

      Section 3.6. Notes Redeemed in Part.

            Any Certificated Security which is to be redeemed only in part shall
be surrendered at the office of the Paying Agent and the Company shall execute
and the Trustee shall authenticate and deliver to the Holder of such Security,
without charge, a new Security or Securities, of any authorized denomination as
requested by such Holder in aggregate principal amount equal to the unredeemed
portion of the Security surrendered.

      Section 3.7. Repayment to the Company.

            To the extent that the aggregate amount of cash deposited by the
Company pursuant to Section 3.5 exceeds the aggregate Redemption Price of the
Notes or portions thereof which the Company is redeeming as of the Redemption
Date, then, promptly after the Redemption Date, the Paying Agent shall return
any such excess to the Company together with interest, if any, thereon.

      Section 3.8. No Sinking Fund.

            The Notes shall not have a sinking fund.

                                   ARTICLE IV

              PURCHASE AT THE OPTION OF HOLDERS ON SPECIFIC DATES

      Section 4.1. Optional Put.

            (a) Each Holder shall have the right, at the Holder's option, but
subject to the provisions of this Section 4.1, to require the Company to
purchase, and upon the exercise of such right, the Company shall purchase, all
of such Holder's Notes not theretofore called for redemption, or any portion of
the principal amount thereof that is equal to $1,000 or an integral multiple
thereof, as directed by such Holder pursuant to this Section 4.1, on each of
March 15, 2011, March 15, 2014 and March 15, 2019 (each a "PURCHASE DATE"). The
Company shall be required to purchase such Notes at a purchase price equal to
100% of the principal amount plus accrued and unpaid interest, Additional
Amounts and Additional Interest, if any, to, but excluding, the Purchase Date
(the "PURCHASE PRICE"). In the event that a Purchase Date is a date that is
after any Regular Record Date but on or before the corresponding Interest
Payment Date,

                                       29
<PAGE>

the Company shall be required to pay accrued and unpaid interest, Additional
Amounts and Additional Interest, if any, to the Holder of the repurchased Note
and not the Holder on the Regular Record Date.

            (b) The Company shall pay the Purchase Price with respect to Notes
to be purchased pursuant to this Article IV as of the first Purchase Date wholly
in cash; however, it may elect with respect to either or both of the two
remaining Purchase Dates to pay the Purchase Price in respect of Notes to be
purchased pursuant to this Section 4.1 as of such Purchase Date, in cash or
Common Stock, or in any combination of cash and Common Stock, subject to the
conditions set forth in Section 4.1(d). The Company shall designate, in the
Company Notice delivered pursuant to this Section 4.1(b), whether the Company
will purchase the Notes for cash or Common Stock, or, if a combination thereof,
the percentages of the Purchase Price of Notes in respect of which it will pay
in cash and Common Stock; provided that the Company shall pay cash for
fractional interests in shares of Common Stock, and it shall pay any accrued and
unpaid interest, Additional Amounts and Additional Interest on such Notes in
cash. Each Holder whose Notes are purchased pursuant to this Section 4.1 shall
receive the same percentage of cash and/or Common Stock in payment of the
Purchase Price for such Notes, except as provided in Section 4.1(d) with regard
to the payment of cash in lieu of fractional interests in shares of Common
Stock. The Company may not change its election with respect to the consideration
(or components or percentages of components thereof) to be paid once the Company
has given its Company Notice to Holders, except as provided in Section 4.1(d).

            No later than 22 Business Days prior to each Purchase Date, the
Company shall mail a written notice (the "COMPANY NOTICE") of the purchase right
by first class mail to the Trustee (and the Paying Agent if the Trustee is not
then acting as a Paying Agent) and to each Holder at its address shown in the
Register of the Registrar, and to beneficial owners as required by applicable
law. The notice shall include a form of Purchase Notice to be completed by the
Holder and shall briefly state, as applicable:

            (i)   the date by which the Purchase Notice must be delivered to the
      Paying Agent in order for a Holder to exercise the purchase right pursuant
      to this Section 4.1;

            (ii)  the Purchase Date;

            (iii) the Purchase Price and, in the case of Notes subject to
      purchase on either the second or third Purchase Date, whether the Company
      will purchase such Notes for cash or Common Stock, or, if a combination
      thereof, the percentages of the Purchase Price of such Notes in respect of
      which it will pay cash and Common Stock;

            (iv)  the name and address of the Paying Agent and the Conversion
      Agent;

            (v)   the Conversion Rate and any adjustments thereto;

            (vi)  that the Notes as to which a Purchase Notice has been given
      may be converted into Common Stock if they are otherwise convertible
      pursuant to ARTICLE XII of this Indenture only if the Purchase Notice has
      been withdrawn in accordance with the terms of this Indenture;

                                       30
<PAGE>

            (vii)  that the Notes must be surrendered to the Paying Agent to
      collect payment;

            (viii) that the Purchase Price for any Notes as to which a Purchase
      Notice has been duly given and not withdrawn shall be paid promptly
      following the later of the Purchase Date and the time of surrender of such
      Security as described in Section 4.1(b)(vii);

            (ix)   the procedures the Holder must follow to exercise its rights
      under this Section 4.1 and a brief description of such rights;

            (x)    briefly, the conversion rights of the Notes, if any, and that
      the Holder must satisfy the requirements set forth in the Indenture in
      order to convert the Notes;

            (xi)   the procedures for withdrawing a Purchase Notice, including a
      form of notice of withdrawal;

            (xii)  that, unless the Company defaults in making payment of such
      Purchase Price, interest (including any Additional Interest) and
      Additional Amounts, if any, on Notes surrendered for purchase by the
      Company shall cease to accrue on and after the Purchase Date; and

            (xiii) the CUSIP number(s) of the Notes.

            In the event the Company has elected to pay a Purchase Price (or a
specified percentage thereof) with Common Stock, the Company Notice shall also:

                  (1)   state that each Holder will receive Common Stock with a
Market Price determined as of a specified date prior to the Purchase Date equal
to a specified percentage of the Purchase Price of the Securities held by such
Holder (except any cash amount to be paid in lieu of a fractional share); and

                  (2)   set forth the method of calculating the Market Price and
state that because the Market Price of Common Stock will be determined prior to
the Purchase Date, the Holders will bear the market risk with respect to the
value of the Common Stock to be received between the date such Market Price is
determined and the Purchase Date.

            At the Company's request, the Trustee shall give the Company Notice
in the Company's name and at the Company's expense; provided, however, that the
Company makes such request at least five Business Days (unless a shorter period
shall be satisfactory to the Trustee) prior to the date by which such Company
Notice must be given to the Holders in accordance with this Section 4.1(b);
provided, further, that the text of the Company Notice shall be prepared by the
Company.

            If any of the Notes is in the form of a Global Security, then the
Company shall modify such Company Notice to the extent necessary to accord with
the procedures of the Depositary applicable to the purchase of Global
Securities.

                                       31
<PAGE>

            Simultaneously with delivering the Company Notice pursuant to this
Section 4.1(b), the Company shall make a Public Notice containing all
information specified in such Company Notice.

            (c) A Holder may exercise its rights specified in clause (a) of this
Section 4.1 upon delivery of a written notice (which shall be in substantially
the form included on the reverse side of the Securities entitled "Option of
Holder to Elect Purchase" hereto and which may be delivered by letter, overnight
courier, hand delivery, facsimile transmission or in any other written form and,
in the case of Global Securities, may be delivered electronically or by other
means in accordance with the Depositary's customary procedures) of the exercise
of such rights (a "PURCHASE NOTICE") to the Paying Agent at any time from the
opening of business on the date that is 22 Business Days prior to the relevant
Purchase Date until the close of business on the second Business Day prior to
such Purchase Date.

            The Purchase Notice delivered by a Holder shall state (i) the
relevant Purchase Date, (ii) if certificated Securities, the serial number or
numbers of the Note or Notes which the Holder shall deliver to be purchased (if
not certificated, the notice must comply with Applicable Procedures), (iii) the
portion of the principal amount of the Note which the Holder shall deliver to be
purchased, which portion must be $1,000 or an integral multiple thereof, and
(iv) that such Note shall be purchased pursuant to the terms and conditions
specified in the Securities and this Indenture.

            Delivery of a Note to the Paying Agent by book-entry transfer or
physical delivery prior to, on or after the applicable Purchase Date (together
with all necessary endorsements) at the offices of the Paying Agent is a
condition to receipt by the Holder of the Purchase Price therefor; provided,
however, that such Purchase Price shall be so paid pursuant to this Section 4.1
only if the Note so delivered to the Paying Agent shall conform in all respects
to the description thereof in the related Purchase Notice, as determined by the
Company.

            The Company shall purchase from the Holder thereof, pursuant to this
Section 4.1, a portion of a Note if the principal amount of such portion is
$1,000 or an integral multiple thereof. Provisions of this Indenture that apply
to the purchase of all of a Note pursuant to Section 4.1 through Section 4.7
also apply to the purchase of such portion of such Note.

            The Paying Agent shall promptly notify the Company of the receipt by
it of any Purchase Notice or written withdrawal thereof.

            Anything herein to the contrary notwithstanding, in the case of
Global Securities, any Purchase Notice may be delivered or withdrawn and such
Securities may be surrendered or delivered for purchase in accordance with the
Applicable Procedures as in effect from time to time.

            (d) To the extent permitted by Section 4.1(b), the Purchase Price of
Notes in respect of which a Purchase Notice pursuant to Section 4.1(c) has been
given, or a specified percentage thereof, may be paid by the Company by the
issuance of a number of shares of Common Stock equal to the quotient obtained by
dividing (i) the amount of cash to which the Holders would have been entitled
had the Company elected to pay all or such specified

                                       32
<PAGE>

percentage, as the case may be, of the Purchase Price of such Securities in cash
by (ii) 95% of the Market Price of a share of Common Stock as of the applicable
Purchase Date, subject to the next succeeding paragraph.

      The Company will not issue a fractional share of Common Stock in payment
of the Purchase Price. Instead the Company will pay cash for the current market
value of the fractional share. The current market value of a fraction of a share
shall be determined by multiplying the Market Price by such fraction and
rounding the product to the nearest whole cent. It is understood that if a
Holder elects to have more than one Security repurchased, the number of shares
of Common Stock shall be based on the aggregate amount of Securities to be
repurchased.

      The Company's right to exercise its election to Purchase Notes pursuant to
this Section 4.1 through the issuance of shares of Common Stock shall be
conditioned upon:

            (i)   the Company having given timely Company Notice of election to
purchase all or a specified percentage of the Notes with Common Stock as
provided in Section 4.1(b);

            (ii)  registration of the shares of Common Stock to be issued in
respect of the payment of the specified percentage of the Purchase Price under
(A) the Exchange Act and (B) the Securities Act, unless in the case of this
clause (B) the shares of Common Stock so issued can be freely resold by the
Holder (assuming such Holder is not the Company or an Affiliate of the Company)
receiving such shares without registration under the Securities Act;

            (iii) any necessary qualification or registration of such shares
under applicable state securities laws or the availability of an exemption from
such qualification and registration;

            (iv)  the Common Stock shall be listed on a national securities
exchange or quoted on an inter-dealer quotation system of any registered
national securities association; and

            (v)   the receipt by the Trustee of an Officers' Certificate and an
Opinion of Counsel each stating that (A) the terms of the issuance of the Common
Stock are in conformity with this Indenture and (B) the shares of Common Stock
to be issued by the Company in payment of the specified percentage of the
Purchase Price in respect of Securities have been duly authorized and, when
issued and delivered pursuant to the terms of this Indenture in payment of the
specified percentage of the Purchase Price in respect of Securities, will be
validly issued, fully paid and nonassessable, and, in the case of such Officers'
Certificate, stating that conditions (i), (ii), (iii) and (iv) above have been
satisfied and, in the case of such Opinion of Counsel, stating that conditions
(ii) and (iii) above have been satisfied.

      Such Officers' Certificate shall also set forth the number of shares of
Common Stock to be issued for each $1,000 principal amount of Notes and the
Closing Sale Price on each Trading Day during the period during which the Market
Price is calculated, and the Company shall disseminate such information as soon
as practicable after determination thereof by Public Notice.

      If conditions are not satisfied prior to or on the Purchase Date and the
Company has elected to purchase the Notes to be purchased as of such Purchase
Date pursuant to this Section

                                       33
<PAGE>

4.1 through the issuance of shares of Common Stock, the Company shall pay the
entire Purchase Price in respect of such Notes in cash.

      Section 4.2. Effect of Purchase Notice; Withdrawal of Purchase Notice.

            (a) Upon receipt by the Paying Agent of the Purchase Notice
specified in Section 4.1(c), the Holder of the Note in respect of which such
Purchase Notice was given shall (unless such Purchase Notice is withdrawn as
specified in the following paragraph) thereafter be entitled to receive solely
the Purchase Price with respect to such Note. Such Purchase Price shall be paid
to such Holder, subject to receipt of cash by the Paying Agent, promptly
following the later of (a) the Purchase Date with respect to such Note (provided
the conditions in Section 4.1(c) have been satisfied) and (b) the time of
book-entry transfer or delivery of such Note to the Paying Agent by the Holder
thereof in the manner required by Section 4.1(c). Notes in respect of which a
Purchase Notice has been given by the Holder thereof may not be converted
pursuant to ARTICLE XII on or after the date of the delivery of such Purchase
Notice unless such Purchase Notice has first been validly withdrawn as specified
in the following paragraph.

            (b) A Purchase Notice may be withdrawn by means of a written notice
(which may be delivered by letter, overnight courier, hand delivery, facsimile
transmission or in any other written form and, in the case of Global Securities,
may be delivered electronically or by other means in accordance with the
Depositary's customary procedures) of withdrawal delivered by the Holder to the
Paying Agent at any time prior to the close of business on the Business Day
immediately preceding the Purchase Date, specifying (a) the principal amount of
the Note or portion thereof (which must be a principal amount of $1,000 or an
integral multiple thereof) with respect to which such notice of withdrawal is
being submitted, (b) if certificated Securities have been issued, the serial
numbers of the withdrawn Notes, or if not certificated, such notice must comply
with Applicable Procedures, and (c) the principal amount, if any, which remains
subject to the Purchase Notice. If a Purchase Notice has been properly withdrawn
pursuant to this Section 4.2(b) prior to the Purchase Date, the Company shall
not be obligated to purchase those Notes so identified in such notice of
withdrawal.

      Section 4.3. Deposit of Purchase Price.

            Prior to 11:00 a.m., New York City time, on the Business Day next
succeeding the applicable Purchase Date, the Company shall irrevocably deposit
with the Paying Agent an amount of cash (in immediately available funds if
deposited on such Business Day) and/or shares of Common Stock (as applicable
under the terms of this ARTICLE IV) sufficient to pay the aggregate Purchase
Price of all the Notes or portions thereof which are to be purchased as of such
Purchase Date.

            If the Paying Agent holds, in accordance with the terms hereof, at
11:00 a.m., New York City time, on the Business Day next succeeding the
applicable Purchase Date, cash and/or shares of Common Stock (as applicable
under the terms of this ARTICLE IV) sufficient to pay the Purchase Price of any
Notes for which a Purchase Notice has been tendered and not withdrawn pursuant
to Section 4.2(b), then, as of such Purchase Date, such Notes shall cease to be
outstanding and interest, Additional Amounts and Additional Interest, if any, on
such Notes shall cease to accrue, whether or not such Notes are delivered to the
Paying Agent, and the rights

                                       34
<PAGE>

of the Holders in respect thereof shall terminate (other than the right to
receive the Purchase Price upon delivery of such Notes).

            The Company shall make a Public Notice of the aggregate principal
amount of Notes purchased on the applicable Purchase Date on such date or as
soon as practicable thereafter.

      Section 4.4. Certificated Securities Purchased in Part.

            Any Certificated Security which is to be purchased only in part
shall be surrendered at the office of the Paying Agent (with, if the Company or
the Trustee so requires, due endorsement by, or a written instrument of transfer
in form satisfactory to the Company and the Trustee duly executed by, the Holder
thereof or such Holder's attorney duly authorized in writing) and promptly after
the applicable Purchase Date the Company shall execute and the Trustee shall
authenticate and deliver to the Holder of such Note, without charge, a new Note
or Notes, of any authorized denomination or denominations as may be requested by
such Holder, in aggregate principal amount equal to, and in exchange for, the
portion of the principal amount of the Note so surrendered that is not
purchased.

      Section 4.5. Covenant to Comply With Securities Laws Upon Purchase of
Securities.

            When complying with the provisions of Section 4.1 hereof (provided
that such offer or purchase constitutes an "issuer tender offer" for purposes of
Rule 13e-4 (which term, as used herein, includes any successor provision
thereto) under the Exchange Act at the time of such offer or purchase), and
subject to any exemptions available under applicable law, the Company shall:

            (a) if applicable, comply with Rule 13e-4 and Rule 14e-1 (or any
successor provision) under the Exchange Act;

            (b) file the related Schedule TO (or any successor schedule, form or
report) if required under the Exchange Act; and

            (c) otherwise comply with all United States federal and state
securities laws so as to permit the rights and obligations under this ARTICLE IV
to be exercised in the time and in the manner specified therein.

      Section 4.6. Repayment to the Company.

            To the extent that the aggregate amount of cash and/or shares of
Common Stock deposited by the Company pursuant to Section 4.3 exceeds the
aggregate Purchase Price of the Notes or portions thereof which the Company is
obligated to purchase as of the applicable Purchase Date, then, promptly after
such Purchase Date, the Paying Agent shall return any such excess to the
Company, together with interest, if any, on any such cash.

      Section 4.7. No Purchase Upon Event of Default. There shall be no purchase
of any Securities pursuant to this ARTICLE IV if there has occurred (prior to,
on or after, as the case may be, the giving by each of the Holders of such Notes
of the required Purchase Notice but, in

                                       35
<PAGE>

any event, prior to the applicable Purchase Date) and is continuing, as of such
Purchase Date, an Event of Default (other than a default in the payment of the
Purchase Price with respect to such Notes). The Paying Agent shall promptly
return to the respective Holders thereof any Notes (a) with respect to which a
Purchase Notice has been delivered in compliance with this Indenture, or (b)
held by it during the continuance of an Event of Default (other than a default
in the payment of the Purchase Price with respect to such Notes), in which case,
upon such return, the Purchase Notice with respect thereto shall be deemed to
have been withdrawn.

                                   ARTICLE V

                       PURCHASE AT THE OPTION OF HOLDERS
                           UPON A FUNDAMENTAL CHANGE

      Section 5.1. Fundamental Change Put.

            (a) In the event that a Fundamental Change shall occur at any time
prior to the Stated Maturity, each Holder shall have the right, at the Holder's
option, but subject to the provisions of this Section 5.1, to require the
Company to purchase, and upon the exercise of such right, the Company shall
purchase, all of such Holder's Notes not theretofore called for redemption, or
any portion of the principal amount thereof that is equal to $1,000 or an
integral multiple thereof, as directed by such Holder pursuant to this Section
5.1, on the date designated by the Company (the "FUNDAMENTAL CHANGE PURCHASE
DATE") that is a Business Day no later than 35 Business Days after the date of
notice pursuant to Section 5.1(b) of the occurrence of a Fundamental Change
(subject to extension to comply with applicable law). The Company shall be
required to purchase such Notes at a purchase price in cash equal to 100% of the
principal amount plus any accrued and unpaid interest, Additional Amounts and
Additional Interest, if any, to, but excluding, the Fundamental Change Purchase
Date (the "FUNDAMENTAL CHANGE PURCHASE Price"). In the event that a Fundamental
Change Purchase Date is a date that is after any Regular Record Date but on or
before the corresponding Interest Payment Date, the Company shall be required to
pay accrued and unpaid interest, Additional Amounts and Additional Interest, if
any, to the Holder of the repurchased Note and not the Holder on the Regular
Record Date.

            (b) No later than 20 days after the occurrence of a Fundamental
Change, the Company shall mail a written notice of the Fundamental Change by
first class mail to the Trustee (and the Paying Agent if the Trustee is not then
acting as Paying Agent) and to each Holder at its address shown in the Register
of the Registrar, and to beneficial owners as required by applicable law. The
notice shall include a form of Fundamental Change Purchase Notice to be
completed by the Holder and shall briefly state, as applicable:

            (i)   the date of such Fundamental Change and, briefly, the events
      causing such Fundamental Change;

            (ii)  the date by which the Fundamental Change Purchase Notice must
      be delivered to the Paying Agent in order for a Holder to exercise the
      purchase right pursuant to this Section 5.1;

                                       36
<PAGE>

            (iii)  the Fundamental Change Purchase Date;

            (iv)   the Fundamental Change Purchase Price;

            (v)    the name and address of the Paying Agent and Conversion
      Agent;

            (vi)   the Conversion Rate and any adjustments thereto;

            (vii)  that the Notes as to which a Fundamental Change Purchase
      Notice has been given may be converted into Common Stock pursuant to
      ARTICLE XII of this Indenture only if the Fundamental Change Purchase
      Notice has been withdrawn in accordance with the terms of this Indenture;

            (viii) that the Notes must be surrendered to the Paying Agent to
      collect payment;

            (ix)   that the Fundamental Change Purchase Price for any Note as to
      which a Fundamental Change Purchase Notice has been duly given and not
      withdrawn shall be paid promptly following the later of the Fundamental
      Change Purchase Date and the time of surrender of such Note as described
      in Section 5.1(b)(viii);

            (x)    the procedures the Holder must follow to exercise rights
      under this Section 5.1 and a brief description of such rights;

            (xi)   the conversion rights of the Notes, and that the Holder must
      satisfy the requirements set forth in the Indenture in order to convert
      the Securities;

            (xii)  the procedures for withdrawing a Fundamental Change Purchase
      Notice, including a form of notice of withdrawal;

            (xiii) that, unless the Company defaults in making payment of such
      Fundamental Change Purchase Price, interest, Additional Amounts and
      Additional Interest, if any, on Notes surrendered for purchase by the
      Company shall cease to accrue on and after the Fundamental Change Purchase
      Date; and

            (xiv)  the CUSIP number(s) of the Notes.

            At the Company's request, the Trustee shall give the notice of
purchase right in the Company's name and at the Company's expense; provided,
however, that the Company makes such request at least five Business Days (unless
a shorter period shall be satisfactory to the Trustee) prior to the date by
which such notice of purchase right must be given to the Holders in accordance
with this Section 5.1(b); provided, further, that the text of the notice of
purchase right shall be prepared by the Company.

            If any of the Notes is in the form of a Global Security, then the
Company shall modify such notice to the extent necessary to accord with the
procedures of the Depositary applicable to the purchase of Global Securities.

                                       37
<PAGE>

            Simultaneously with delivering the written notice pursuant to this
Section 5.1(b), the Company shall make a Public Notice containing all
information specified in such written notice.

            (c) A Holder may exercise its rights specified in clause (a) of this
Section 5.1 upon delivery of a written notice (which shall be in substantially
the form included on the reverse side of the Notes entitled "Option of Holder to
Elect Purchase" hereto and which may be delivered by letter, overnight courier,
hand delivery, facsimile transmission or in any other written form and, in the
case of Global Securities, may be delivered electronically or by other means in
accordance with the Applicable Procedures) of the exercise of such rights (a
"FUNDAMENTAL CHANGE PURCHASE NOTICE") to the Paying Agent at any time on or
before the 20th Business Day after the date of the Company's notice of the
Fundamental Change (subject to extension to comply with applicable law).

            The Fundamental Change Purchase Notice delivered by a Holder shall
state (i) the Fundamental Change Purchase Date, (ii) if certificated Securities,
the serial number or numbers of the Note or Notes which the Holder shall deliver
to be purchased (if not certificated, the notice must comply with Applicable
Procedures), (iii) the portion of the principal amount of the Note which the
Holder shall deliver to be purchased, which portion must be $1,000 or an
integral multiple thereof, and (iv) that such Note shall be purchased pursuant
to the terms and conditions specified in the Securities and this Indenture.

            Delivery of a Note (together with all necessary endorsements) to the
Paying Agent by book-entry transfer or physical delivery prior to, on or after
the Fundamental Change Purchase Date at the offices of the Paying Agent is a
condition to receipt by the Holder of the Fundamental Change Purchase Price
therefor; provided, however, that such Fundamental Change Purchase Price shall
be so paid pursuant to this Section 5.1 only if the Note so delivered to the
Paying Agent shall conform in all respects to the description thereof in the
related Fundamental Change Purchase Notice, as determined by the Company.

            The Company shall purchase from the Holder thereof, pursuant to this
Section 5.1, a portion of a Note if the principal amount of such portion is
$1,000 or an integral multiple thereof. Provisions of the Indenture that apply
to the purchase of all of a Note also apply to the purchase of such portion of
such Note.

            A Paying Agent shall promptly notify the Company of the receipt by
it of any Fundamental Change Purchase Notice or written withdrawal thereof.

            Anything herein to the contrary notwithstanding, in the case of
Global Securities, any Fundamental Change Purchase Notice may be delivered or
withdrawn and such Notes may be surrendered or delivered for purchase in
accordance with the Applicable Procedures as in effect from time to time.

            (d) Not more than 30 days after the occurrence of a Fundamental
Change, the Company shall use its best efforts to either (i) obtain the consents
under all existing indebtedness required to permit the repurchase of the Notes
pursuant to any Fundamental Change Purchase Notice or (ii) repay in full all
existing indebtedness and terminate all commitments under all

                                       38
<PAGE>

existing indebtedness, in each case the terms of which would prohibit the
purchase of the Notes pursuant to any Fundamental Change Purchase Notice.

      Section 5.2. Effect of Fundamental Change Purchase Notice.

            (a) Upon receipt by the Paying Agent of the Fundamental Change
Purchase Notice specified in Section 5.1(c), the Holder of the Note in respect
of which such Fundamental Change Purchase Notice was given shall (unless such
Fundamental Change Purchase Notice is withdrawn as specified in the following
paragraph) thereafter be entitled to receive the Fundamental Change Purchase
Price with respect to such Note. Such Fundamental Change Purchase Price shall be
paid to such Holder, subject to receipt of cash by the Paying Agent, promptly
following the later of (a) the Fundamental Change Purchase Date with respect to
such Note (provided the conditions in Section 5.1(c) have been satisfied) and
(b) the time of book-entry transfer or delivery of such Note to the Paying Agent
by the Holder thereof in the manner required by Section 5.1(c). Notes in respect
of which a Fundamental Change Purchase Notice has been given by the Holder
thereof may not be converted pursuant to ARTICLE XII on or after the date of the
delivery of such Fundamental Change Purchase Notice unless such Fundamental
Change Purchase Notice has first been validly withdrawn as specified in the
following paragraph.

            (b) A Fundamental Change Purchase Notice may be withdrawn by means
of a written notice (which may be delivered by letter, overnight courier, hand
delivery, facsimile transmission or in any other written form and, in the case
of Global Securities, may be delivered electronically or by other means in
accordance with the Depositary's customary procedures) of withdrawal delivered
by the Holder to the Paying Agent at any time prior to the close of business on
the Business Day immediately preceding the Fundamental Change Purchase Date,
specifying (a) the principal amount of the Note or portion thereof (which must
be a principal amount of $1,000 or an integral multiple thereof) with respect to
which such notice of withdrawal is being submitted, (b) if certificated Notes
have been issued, the serial numbers of the withdrawn Notes, or if not
certificated, such notice must comply with Applicable Procedures, and (c) the
principal amount, if any, which remains subject to the Fundamental Change
Purchase Notice. If a Fundamental Change Purchase Notice has been properly
withdrawn pursuant to this Section 5.2(b) prior to the Fundamental Change
Purchase Date, the Company shall not be obligated to purchase those Notes so
identified in such notice of withdrawal.

      Section 5.3. Deposit of Fundamental Change Purchase Price.

            Prior to 11:00 a.m., New York City time, on the Business Day
immediately succeeding the applicable Fundamental Change Purchase Date, the
Company shall irrevocably deposit with the Paying Agent an amount of cash (in
immediately available funds if deposited on such Business Day) sufficient to pay
the aggregate Fundamental Change Purchase Price of all the Notes or portions
thereof which are to be purchased as of such Fundamental Change Purchase Date.

            If the Paying Agent holds, in accordance with the terms hereof, at
11:00 a.m., New York City time, on the Business Day immediately succeeding the
applicable Fundamental Change Purchase Date, cash sufficient to pay the
Fundamental Change Purchase Price of any

                                       39
<PAGE>

Notes for which a Fundamental Change Purchase Notice has been tendered and not
withdrawn pursuant to Section 5.2(b), then, as of such Fundamental Change
Purchase Date, such Notes shall cease to be outstanding and interest, Additional
Amounts and Additional Interest, if any, on such Notes shall cease to accrue,
whether or not such Notes are delivered to the Paying Agent, and the rights of
the Holders in respect thereof shall terminate (other than the right to receive
the Fundamental Change Purchase Price upon delivery of such Notes).

            The Company shall make a Public Notice of the aggregate principal
amount of Notes purchased as a result of such Fundamental Change on or as soon
as practicable after the Fundamental Change Purchase Date.

      Section 5.4. Certificated Securities Purchased in Part.

            Any Certificated Security that is to be purchased only in part shall
be surrendered at the office of the Paying Agent (with, if the Company or the
Trustee so requires, due endorsement by, or a written instrument of transfer in
form satisfactory to the Company and the Trustee duly executed by, the Holder
thereof or such Holder's attorney duly authorized in writing) and promptly after
the Fundamental Change Purchase Date the Company shall execute and the Trustee
shall authenticate and deliver to the Holder of such Note, without charge, a new
Note or Notes, of any authorized denomination or denominations as may be
requested by such Holder, in aggregate principal amount equal to, and in
exchange for, the portion of the principal amount of the Note so surrendered
that is not purchased.

      Section 5.5. Covenant to Comply With Securities Laws Upon Purchase of
Notes.

            When complying with the provisions of Section 5.1 hereof (provided
that such offer or purchase constitutes an "issuer tender offer" for purposes of
Rule 13e-4 (which term, as used herein, includes any successor provision
thereto) under the Exchange Act at the time of such offer or purchase), and
subject to any exemptions available under applicable law, the Company shall:

            (a) if applicable, comply with Rule 13e- 4 and Rule 14e-1 (or any
successor provision) under the Exchange Act;

            (b) file the related Schedule TO (or any successor schedule, form or
report) if required under the Exchange Act; and

            (c) otherwise comply with all United States federal and state
securities laws so as to permit the rights and obligations under this ARTICLE V
to be exercised in the time and in the manner specified therein.

      Section 5.6. Repayment to the Company.

            To the extent that the aggregate amount of cash deposited by the
Company pursuant to Section 5.3 exceeds the aggregate Fundamental Change
Purchase Price of the Notes or portions thereof which the Company is obligated
to purchase as of the Fundamental Change Purchase Date then, promptly after the
Fundamental Change Purchase Date, the Paying Agent shall return any such excess
to the Company together with interest, if any, thereon.

                                       40
<PAGE>

                                   ARTICLE VI

                                   COVENANTS

      Section 6.1. Payment of Notes.

            The Company shall pay interest on the Notes as provided in the
Notes. The Company shall promptly make all payments in respect of the Notes on
the dates and in the manner provided in the Notes or pursuant to this Indenture.
Principal Amount, Redemption Price, Purchase Price and Fundamental Change
Purchase Price and accrued and unpaid interest, Additional Amounts and
Additional Interest, if any, shall be considered paid on the applicable date due
if by 11:00 a.m., New York City time, on such date the Paying Agent holds, in
accordance with this Indenture, cash or securities, if permitted hereunder,
sufficient to pay all such amounts then due. The Company shall, to the fullest
extent permitted by law, pay interest on overdue principal and overdue
installments of interest, Additional Amounts and Additional Interest, if any, at
the rate borne by the Notes per annum plus 1%. All references in this Indenture
or the Notes to interest shall, without duplication, be deemed to include
Additional Amounts and Additional Interest, if any, payable pursuant to the
Registration Rights Agreement.

            If at any time Additional Interest becomes payable by the Company
pursuant to the Registration Rights Agreement, the Company shall promptly
deliver to the Trustee a certificate to that effect and stating (i) the amount
of such Additional Interest that is payable and (ii) the date on which such
Additional Interest is payable pursuant to the terms of the Registration Rights
Agreement. Unless and until a Responsible Officer of the Trustee receives such a
certificate, the Trustee may assume without inquiry that no Additional Interest
is payable. If the Company has paid Additional Interest directly to the Persons
entitled to it, the Company shall deliver to the Trustee a certificate setting
forth the particulars of such payment.

            Each payment of the principal of and interest, Additional Amounts
and Additional Interest, if any, on the Notes due in cash shall be in such coin
or currency of the United States of America as at the time of payment is legal
tender for payment of public and private debts.

            Subject to Section 3.1, Section 4.1 and Section 5.1, the Company
shall pay interest, Additional Amounts and Additional Interest, if any, on the
Notes to the Person in whose name the Notes are registered at the close of
business on the Regular Record Date next preceding the corresponding Interest
Payment Date. Any such interest, Additional Amounts and Additional Interest, if
any, not so punctually paid or duly provided for shall forthwith cease to be
payable to the Holder on such Regular Record Date and may be paid (a) to the
Person in whose name the Notes are registered at the close of business on a
Special Record Date for the payment of such defaulted interest, Additional
Amounts and Additional Interest, if any, to be fixed by the Trustee, notice
whereof shall be given to the Holders not less than 10 calendar days prior to
such Special Record Date or (b) at any time in any other lawful manner not
inconsistent with the requirements of any securities exchange on which the Notes
may be listed, and upon such notice as may be required by such exchange.

            The Holder must surrender the Notes to the Paying Agent to collect
payment of principal. Payment of cash interest, Additional Amounts and
Additional Interest, if any, on

                                       41
<PAGE>

Certificated Securities in the aggregate principal amount of $5,000,000 or less
shall be made by check mailed to the address of the Person entitled thereto as
such address appears in the Register, and payment of cash interest, Additional
Amounts and Additional Interest, if any, on Certificated Securities in aggregate
principal amount in excess of $5,000,000 shall be made by wire transfer in
immediately available funds at the election of such Holder. Notwithstanding the
foregoing, so long as the Notes are registered in the name of a Depositary or
its nominee, all payments with respect to the Notes shall be made by wire
transfer of immediately available funds to the account of the Depositary or its
nominee. At the Stated Maturity, interest, Additional Amounts and Additional
Interest, if any, on Certificated Securities will be payable at the office or
agency of the Company described in Section 6.5.

      Section 6.2. SEC and Other Reports to the Trustee.

            (a) The Company shall ensure delivery to the Trustee within 15
calendar days after it files such annual and quarterly reports, information,
documents and other reports with the SEC, copies of its annual report and of the
information, documents and other reports (or copies of such portions of any of
the foregoing as the SEC may by rules and regulations prescribe) which the
Company is required to file with the SEC pursuant to Section 13 or 15(d) of the
Exchange Act in accordance with TIA Section 314(a). In the event the Company is
at any time no longer subject to the reporting requirements of Section 13 or
15(d) of the Exchange Act, it shall continue to provide the Trustee with reports
containing substantially the same information as would have been required to be
filed with the SEC had the Company continued to have been subject to such
reporting requirements. In such event, such reports shall be provided at the
times the Company would have been required to provide reports had it continued
to have been subject to such reporting requirements. The Company also shall
comply with the other provisions of TIA Section 314(a). Delivery of such
reports, information and documents to the Trustee is for informational purposes
only and the Trustee's receipt of such shall not constitute constructive notice
of any information contained therein or determinable from information contained
therein, including the Company's compliance with any of its covenants hereunder
(as to which the Trustee is entitled to rely conclusively on Officers'
Certificates). The Trustee shall have no duty or responsibility to review such
reports, information or documents.

            (b) The Company may deliver the reports referred to in paragraph (a)
above in this Section 6.2 by delivering copies to the Trustee either (i) in
accordance with the methods set forth in Section 13.2 or (ii) in electronic
format at an email address provided by the Trustee. Delivery of the reports,
information and documents to the Trustee pursuant to this Section 6.2(b) shall
be solely for the purposes of compliance with this Section 6.2(b) and with TIA
Section 314(a). The Trustee's receipt of such reports, information and documents
shall not constitute notice to it of the consent thereof or of any matter
determinable from the content thereof, including the Company's compliance with
any of its covenants hereunder, as to which the Trustee is entitled to rely upon
Officers' Certificates.

      Section 6.3. Compliance Certificate.

            The Company shall deliver to the Trustee within 120 calendar days
after the end of each fiscal year of the Company, beginning with the fiscal year
ending December 31, 2004, an

                                       42
<PAGE>

Officers' Certificate, stating whether or not to the knowledge of the signers
thereof, the Company is in compliance with all conditions and covenants under
this Indenture.

      Section 6.4. Further Instruments and Acts.

            Upon request of the Trustee, or as otherwise necessary, the Company
shall execute and deliver such further instruments and do such further acts as
may be reasonably necessary or proper to carry out more effectively the purposes
of this Indenture.

      Section 6.5. Maintenance of Office or Agency of the Trustee, Registrar,
Paying Agent and Conversion Agent.

            The Company shall maintain in the Borough of Manhattan, New York,
New York, an office or agency of the Trustee, Registrar, Paying Agent and
Conversion Agent where Notes may be presented or surrendered for payment, where
Notes may be surrendered for registration of transfer, exchange, redemption,
repurchase or conversion and where notices and demands to or upon the Company in
respect of the Notes and this Indenture may be served. The office of JPMorgan
Chase Bank located in New York City at 4 New York Plaza, Floor 15, New York, New
York 10004, shall initially be such office or agency for all of the aforesaid
purposes. The Company shall give prompt written notice to the Trustee of the
location, and of any change in the location, of any such office or agency (other
than a change in the location of the office of the Trustee). If at any time the
Company shall fail to maintain any such required office or agency or shall fail
to furnish the Trustee with the address thereof, such presentations, surrenders,
notices and demands may be made or served at the address of the Trustee set
forth in Section 13.2.

            The Company may also from time to time designate one or more other
offices or agencies where the Notes may be presented or surrendered for any or
all such purposes and may from time to time rescind such designations; provided,
however, that no such designation or rescission shall in any manner relieve the
Company of its obligation to maintain an office or agency in the Borough of
Manhattan, New York, New York, for such purposes.

      Section 6.6. Delivery of Information Required Under Rule 144A.

            Upon the request of a Holder or any beneficial owner of Notes or
holder or beneficial owner of Common Stock issued upon conversion thereof, the
Company shall promptly furnish or cause to be furnished the information required
pursuant to Rule 144A(d)(4) under the Securities Act to such Holder or any
beneficial owner of Securities or holder or beneficial owner of Common Stock, or
to a prospective purchaser of any such security designated by any such holder,
as the case may be, to the extent required to permit compliance by such Holder
or holder with Rule 144A under the Securities Act in connection with the resale
of any such security. Whether a person is a beneficial owner shall be determined
by the Company to the Company's reasonable satisfaction.

      Section 6.7. Waiver of Stay, Extension or Usury Laws.

            The Company covenants (to the extent that it may lawfully do so)
that it shall not at any time insist upon, or plead, or in any manner whatsoever
claim or take the benefit or

                                       43
<PAGE>

advantage of, any stay or extension law or any usury or other law wherever
enacted, now or at any time hereafter in force, which would prohibit or forgive
the Company from paying all or any portion of the principal amount, Redemption
Price, Purchase Price or Fundamental Change Purchase Price in respect of Notes,
or any interest, Additional Amounts and Additional Interest, if any, on such
amounts, as contemplated herein, or which may affect the covenants or the
performance of this Indenture; and the Company (to the extent that it may
lawfully do so) hereby expressly waives all benefit or advantage of any such
law, and covenants that it shall not hinder, delay or impede the execution of
any power herein granted to the Trustee, but shall suffer and permit the
execution of every such power as though no such law had been enacted.

      Section 6.8. Statement by Officers as to Default.

            The Company shall deliver to the Trustee, as soon as practicable and
in any event within five Business Days after the Company becomes aware of the
occurrence of any Default or Event of Default, an Officers' Certificate setting
forth the details of such Default or Event of Default and the action which the
Company proposes to take with respect thereto.

      Section 6.9. Payment of Additional Amounts.

            Unless otherwise required by Panamanian law, the Company will not
deduct or withhold from payments made with respect to the Securities on account
of any present or future Taxes. In the event that Company is required to
withhold or deduct on account of any Taxes due from any payment made under or
with respect to the Securities, the Company will pay such additional amounts
("ADDITIONAL AMOUNTS") as may be necessary so that the net amount received by
each Holder of Securities will equal the amount that the Holder would have
received if the Taxes had not been required to be withheld or deducted; provided
that no Additional Amounts will be payable with respect to a payment made to a
Holder (an "EXCLUDED HOLDER") to the extent: (i) that any Taxes would not have
been so imposed but for the existence of any present or former connection
between the Holder and Panama, other than the mere receipt of the payment,
acquisition, ownership or disposition of such Securities or the exercise or
enforcement of rights under the Securities or this Indenture; (ii) of any
estate, inheritance, gift, sales, transfer or personal property Taxes imposed
with respect to the Securities, except as described below or as otherwise
provided in this Indenture; (iii) that any such Taxes would not have been
imposed but for the presentation of the Securities, where presentation is
required, for payment on a date more than 30 days after the date on which the
payment became due and payable or the date on which payment thereof is duly
provided for, whichever is later, except to the extent that the beneficiary or
Holder thereof would have been entitled to Additional Amounts had the Securities
been presented for payment on any date during such 30-day period; or (iv) that
the Holder would not be liable or subject to such withholding or deduction of
Taxes but for the failure to make a valid declaration of non-residence or other
similar claim for exemption, if: (a) the making of the declaration or claim is
required or imposed by statute, treaty, regulation, ruling or administrative
practice of the relevant taxing authority as a precondition to an exemption
from, or reduction in, the relevant Taxes; and (b) at least 60 days prior to the
first payment date with respect to which the Company shall apply this clause
(iv), the Company shall have notified all Holders of the Securities in writing
that they shall be required to provide this declaration or claim. The Company
shall also (i) withhold or deduct such Taxes as required; (ii) remit the full
amount of Taxes deducted or withheld to the relevant taxing authority in
accordance with all applicable

                                       44
<PAGE>

laws; (iii) use reasonable efforts to obtain from each relevant taxing authority
imposing the Taxes certified copies of tax receipts evidencing the payment of
any Taxes deducted or withheld; and (iv) upon request, make available to the
Holders of the Securities, within 60 days after the date the payment of any
Taxes deducted or withheld is due pursuant to applicable law, certified copies
of tax receipts evidencing such payment by the Company and, notwithstanding the
Company's efforts to obtain the receipts, if the same are not obtainable, other
evidence of such payments.

            In addition, the Company will pay any stamp, issue, registration,
documentary or other similar taxes and duties, including interest, penalties and
additional amounts with respect thereto, payable in Panama or the United States,
or any political subdivision or taxing authority of or in the foregoing with
respect to the creation, issue, offering, enforcement, redemption or retirement
of the Securities.

            At least 30 days prior to each date on which any payment under or
with respect to the Securities is due and payable, if the Company becomes
obligated to pay Additional Amounts with respect to such payment, the Company
shall deliver to the Trustee an Officers' Certificate stating the fact that such
Additional Amounts will be payable, and the amounts so payable and will set
forth such other information as is necessary to enable the Trustee to pay such
Additional Amounts to the Holders on the payment date. Whenever in this
Indenture there is mentioned, in any context, the payment of principal or
interest (including Additional Interest and defaulted interest) or any other
amount payable on or with respect to any of the Securities, such mention shall
be deemed to include mention of the payment of Additional Amounts provided for
in this Section 6.9 to the extent that, in such context, Additional Amounts are,
were or would be payable in respect thereof pursuant to the provisions of this
Section 6.9 and express mention of the payment of Additional Amounts in those
provisions hereof shall not be construed as excluding Additional Amounts in
those provisions hereof where such express mention is not made (if applicable).

            If payments with respect to the Securities become subject generally
to the taxing jurisdiction of any Territory or any political subdivision or
taxing authority thereof or therein having power to tax, other than or in
addition to Panama or any political subdivision or taxing authority therein or
thereof having power to tax, immediately upon becoming aware thereof the Company
shall notify the Trustee of such event, and thereupon the Company shall be
obligated to pay Additional Amounts in respect thereof on terms corresponding to
the terms of the foregoing provisions of this Section 6.9 with the substitution
for (or, as the case may be, in addition to) the references herein to Panama or
any political subdivision or authority therein or thereof having power to tax of
references to that other or additional Territory or any political subdivision or
authority therein or thereof having power to tax to whose taxing jurisdiction
such payments shall have become subject as aforesaid. The term "TERRITORY" means
for this purpose any jurisdiction in which the Company is incorporated or in
which it has its place of central management or central control.

            The obligations of the Company under this Section 6.9 shall survive
the termination of this Indenture and the payment of all amounts under or with
respect to this Indenture and the Securities.

                                       45
<PAGE>

      Section 6.10. Indemnification for Foreign Currency Judgments.

            The obligations of the Company to any Holder or the Trustee shall,
notwithstanding any judgment in a currency (the "JUDGMENT CURRENCY") other than
United States Dollars (the "AGREEMENT CURRENCY"), be discharged only to the
extent that on the first Business Day following receipt by such Holder or the
Trustee, as the case may be, of any amount in the Judgment Currency, such Holder
or the Trustee may in accordance with normal banking procedures purchase the
Agreement Currency with the Judgment Currency in the City of New York. If the
amount of the Agreement Currency that could be so purchased is less than the
amount originally to be paid to such Holder or the Trustee, as the case may be,
in the Agreement Currency, the Company agrees, as a separate obligation and
notwithstanding such judgment, to pay to such Holder or the Trustee, as the case
may be, the difference, and if the amount of the Agreement Currency that could
be so purchased exceeds the amount originally to be paid to such Holder or the
Trustee, as the case may be, such Holder or the Trustee, as the case may be,
shall pay to or for the account of the Company such excess, provided that such
Holder or the Trustee, as the case may be, shall not have any obligation to pay
any such excess as long as a Default in respect of the obligations of the
Company to pay when due any amounts due under this Indenture has occurred and is
continuing, in which case such excess may be applied by such Holder or the
Trustee, as the case may be, to such payment obligations.

                                  ARTICLE VII

                             SUCCESSOR CORPORATION

      Section 7.1. When Company May Merge or Transfer Assets.

            The Company shall not consolidate with or merge with or into any
other person or convey, transfer, sell, lease or otherwise dispose of all or
substantially all of its properties and assets to any person, unless:

            (a) either (i) the Company shall be the continuing corporation or
(ii) the Person (if other than the Company) formed by such consolidation or into
which the Company is merged or the Person which acquires by conveyance,
transfer, sale, lease or other disposition all or substantially all of the
properties and assets of the Company (1) shall be a corporation organized and
validly existing under the laws of the United States or any State thereof or the
District of Columbia, Panama or The Netherlands (even if a Subsidiary of another
Person) and (2) shall expressly assume, by an indenture supplemental hereto,
executed and delivered to the Trustee, in form reasonably satisfactory to the
Trustee, all of the obligations of the Company under the Notes, this Indenture
and the Registration Rights Agreement and, to the extent applicable, otherwise
comply with the provisions of Section 12.4;

            (b) immediately before and after giving effect to such transaction,
no Default shall have occurred and be continuing; and

            (c) the Company shall have delivered to the Trustee an Officers'
Certificate and an Opinion of Counsel, each stating that such consolidation,
merger, conveyance, transfer, sale, lease or other disposition and, if a
supplemental indenture is required in connection with such

                                       46
<PAGE>

transaction, such supplemental indenture, comply with this ARTICLE VII and that
all conditions precedent herein provided for relating to such transaction have
been satisfied.

            For purposes of the foregoing, the transfer (by lease, assignment,
sale or otherwise) of the properties and assets of one or more Subsidiaries,
which, if such assets were owned by the Company, together with the assets of all
of the other Subsidiaries of the Company, would constitute all or substantially
all of the properties and assets of the Company, shall be deemed to be the
transfer of all or substantially all of the properties and assets of the Company
unless such transfer is to the Company or another Subsidiary.

            The successor Person formed by such consolidation or into which the
Company is merged or the successor Person to which such conveyance, transfer,
sale, lease or other disposition is made shall succeed to, and be substituted
for, and may exercise every right and power of, the Company under this Indenture
with the same effect as if such successor had been named as the Company herein;
and thereafter, except in the case of a lease, the Company shall be discharged
from all obligations and covenants under this Indenture, the Notes and the
Registration Rights Agreement. Subject to Section 11.6, the Company, the Trustee
and the successor Person shall enter into a supplemental indenture to evidence
the succession and substitution of such successor Person and such discharge and
release of the Company.

                                  ARTICLE VIII

                             DEFAULTS AND REMEDIES

      Section 8.1. Events of Default.

            So long as any Notes are outstanding, each of the following shall be
an "EVENT OF DEFAULT":

            (a) the failure by the Company to pay the principal of any Note when
the same becomes due and payable as therein provided or as provided in this
Indenture;

            (b) the failure by the Company to pay any accrued and unpaid
interest, Additional Amounts or Additional Interest, if any, on any Note, in
each case, when due and payable, and such default shall continue for a period of
30 days;

            (c) the failure by the Company to convert any portion of any Note
following the exercise by the Holder of the right to convert such Note into
Common Stock (or cash or a combination of cash and Common Stock, if the Company
elects) pursuant to and in accordance with ARTICLE XII;

            (d) the failure by the Company to redeem any Note, or any portion
thereof, called for redemption by the Company pursuant to and in accordance with
ARTICLE III and;

            (e) the failure by the Company to provide notice in the event of a
Fundamental Change in accordance with Section 5.1(b);

                                       47
<PAGE>

            (f) the failure by the Company to purchase any Note, or any portion
thereof, in accordance with ARTICLE IV or ARTICLE V, upon the exercise by the
Holder of such Holder's right to require the Company to purchase such Notes
pursuant thereto;

            (g) the failure by the Company to perform or observe any other term,
covenant or agreement contained in the Securities or the Indenture (other than a
term, covenant or agreement a default in whose performance or whose breach is
elsewhere in this Section 8.1 specifically dealt with) for a period of 60 days
after written notice of such failure has been given, by certified mail, (1) to
the Company by the Trustee or (2) to the Company and the Trustee by the Holders
of at least 25% in aggregate principal amount of the Securities then
outstanding;

            (h) there shall have occurred a default under any credit agreement,
mortgage, indenture or instrument under which there may be issued or by which
there may be secured or evidenced any Indebtedness of the Company or any of its
Subsidiaries for money borrowed, whether such Indebtedness now exists, or is
created after the date of this Indenture, which default (i) involves the failure
to pay principal of or any premium or interest on such Indebtedness when such
Indebtedness becomes due and payable at the stated maturity thereof, and such
default shall continue after any applicable grace period or (ii) results in the
acceleration of such Indebtedness prior to the stated maturity thereof (without
such acceleration being rescinded or annulled) and, in each case, the principal
amount of any such Indebtedness, together with the principal amount of any other
such Indebtedness so unpaid at its stated maturity or the stated maturity of
which has been so accelerated, aggregates $10,000,000 or more;

            (i) there shall be a failure by the Company or any of its
Subsidiaries to pay final judgments not covered by insurance aggregating in
excess of $7,500,000, which judgments are not paid, discharged or stayed for a
period of 60 days; and

            (j) the Company or any Significant Subsidiary, or any group of two
or more Subsidiaries that, taken as a whole, would constitute a Significant
Subsidiary, pursuant to or under or within the meaning of any Bankruptcy Law:

            (i)   commences a voluntary case or proceeding;

            (ii)  consents to the entry of any order for relief against it in an
      involuntary case or proceeding or the commencement of any case against it;

            (iii) consents to the appointment of a Custodian of it or for any
      substantial part of its property;

            (iv)  makes a general assignment for the benefit of its creditors;

            (v)   files a petition in bankruptcy or answer or consent seeking
      reorganization or relief; or

            (vi)  consents to the filing of such petition or the appointment of
      or taking possession by a Custodian; or

                                       48
<PAGE>

            (k) a court of competent jurisdiction enters an order or decree
under any Bankruptcy Law that:

            (i)   is for relief against the Company or any Significant
      Subsidiary in an involuntary case or proceeding, or adjudicates the
      Company or any Significant Subsidiary insolvent or bankrupt;

            (ii)  appoints a Custodian of the Company or any Significant
      Subsidiary or for any substantial part of the property of either; or

            (iii) orders the winding up or liquidation of the Company or any
      Significant Subsidiary, and the order of decree remains unstayed and in
      effect for 60 days.

      Section 8.2. Acceleration.

            If an Event of Default (other than an Event of Default specified in
Section 8.1(j) or Section 8.1(k) with respect to the Company) occurs and is
continuing (including an Event of Default specified in Section 8.1(j) or Section
8.1(k) with respect to one or more Significant Subsidiaries), the Trustee by
notice to the Company, or the Holders of at least 25% in aggregate principal
amount of the Notes at the time outstanding by notice to the Company and the
Trustee, may declare the principal amount plus accrued and unpaid interest,
Additional Amounts and Additional Interest, if any, on all the Notes to be
immediately due and payable. Upon such a declaration, such accelerated amount
shall be due and payable immediately.

            If an Event of Default specified in Section 8.1(j) or Section 8.1(k)
occurs with respect to the Company and is continuing, the principal amount plus
accrued and unpaid interest, Additional Amounts and Additional Interest, if any,
on all the Notes shall become and be immediately due and payable without any
declaration or other act on the part of the Trustee or any Holders.

            The Holders of a majority in aggregate principal amount of the Notes
at the time outstanding, by notice to the Trustee (and without notice to any
other Holder) may rescind an acceleration and its consequences if the rescission
would not conflict with any judgment or decree of a court of competent
jurisdiction and if all existing Events of Default have been cured or waived
except nonpayment of the principal amount plus accrued and unpaid interest,
Additional Amounts and Additional Interest, if any, that have become due solely
as a result of acceleration and if all amounts due to the Trustee under Section
9.7 have been paid. No such rescission shall affect any subsequent Default or
impair any right consequent thereto.

      Section 8.3. Other Remedies.

            If an Event of Default occurs and is continuing, the Trustee may,
but shall not be obligated to, pursue any available remedy to collect the
payment of the principal plus accrued and unpaid interest, Additional Amounts
and Additional Interest, if any, on the Notes or to enforce the performance of
any provision of the Notes or this Indenture.

            The Trustee may maintain a proceeding even if the Trustee does not
possess any of the Notes or does not produce any of the Notes in the proceeding.
A delay or omission by the

                                       49
<PAGE>

Trustee or any Holder in exercising any right or remedy accruing upon an Event
of Default shall not impair the right or remedy or constitute a waiver of, or
acquiescence in, the Event of Default. No remedy is exclusive of any other
remedy. All available remedies are cumulative.

      Section 8.4. Waiver of Past Defaults.

            Subject to Section 8.7 and Section 11.2, the Holders of a majority
in aggregate principal amount of the Notes at the time outstanding, by notice to
the Trustee (and without notice to any other Holder), may waive an existing
Default and its consequences except:

            (a) a Default described in Section 8.1(a), Section 8.1(b), Section
8.1(d) or Section 8.1(f);

            (b) a Default which constitutes a failure to convert any Note in
accordance with the terms of ARTICLE XII; or

            (c) a Default in respect of any provision of this Indenture or the
Notes, which, under Section 11.2, cannot be amended or modified without the
consent of each Holder affected thereby.

            When a Default is waived, it is deemed cured, but no such waiver
shall extend to any subsequent or other Default or impair any consequent right.
This Section 8.4 shall be in lieu of Section 316(a)1(B) of the TIA and such
Section 316(a)1(B) is hereby expressly excluded from this Indenture, as
permitted by the TIA.

      Section 8.5. Control by Majority.

            The Holders of a majority in aggregate principal amount of the Notes
at the time outstanding may direct the time, method and place of conducting any
proceeding for any remedy available to the Trustee or of exercising any trust or
power conferred on the Trustee. However, the Trustee may refuse to follow any
direction that conflicts with law or this Indenture or that the Trustee
determines in good faith is prejudicial to the rights of other Holders or would
involve the Trustee in personal liability unless the Trustee is offered
indemnity satisfactory to it. This Section 8.5 shall be in lieu of Section
316(a)1(A) of the TIA and such Section 316(a)1(A) is hereby expressly excluded
from this Indenture, as permitted by the TIA.

      Section 8.6. Limitation on Suits.

            A Holder may not pursue any remedy with respect to this Indenture or
the Securities unless:

            (a) the Holder gives to the Trustee written notice stating that an
Event of Default is continuing;

            (b) the Holders of at least 25% in aggregate principal amount of the
Notes at the time outstanding make a written request to the Trustee to pursue
the remedy;

                                       50
<PAGE>

            (c) such Holder or Holders offered to the Trustee security or
indemnity satisfactory to the Trustee against any loss, liability or expense;

            (d) the Trustee does not comply with the request within 60 days
after receipt of such notice, request and offer of security or indemnity; and

            (e) the Holders of a majority in aggregate principal amount of the
Notes at the time outstanding do not give the Trustee a direction inconsistent
with the request during such 60-day period.

            A Holder may not use this Indenture to prejudice the rights of any
other Holder or to obtain a preference or priority over any other Holder.

      Section 8.7. Rights of Holders to Receive Payment or to Convert.

            Notwithstanding any other provision of this Indenture, the right of
any Holder to receive payment of the principal amount, Redemption Price,
Purchase Price, Fundamental Change Purchase Price, interest, Additional Amounts
and Additional Interest, if any, in respect of the Notes held by such Holder, on
or after the respective due dates expressed in the Securities and in this
Indenture, and to convert such Notes in accordance with ARTICLE XII, or to bring
suit for the enforcement of any such payment on or after such respective dates
or the right to convert, is absolute and unconditional and shall not be impaired
or affected adversely without the consent of such Holder.

      Section 8.8. Collection Suit by Trustee.

            If an Event of Default described in Section 8.1(a), Section 8.1(b),
Section 8.1(d) or Section 8.1(f) occurs and is continuing, the Trustee may
recover judgment in its own name and as trustee of an express trust against the
Company or another obligor on the Notes for the whole amount owing with respect
to the Securities and the amounts provided for in Section 9.7.

      Section 8.9. Trustee May File Proofs of Claim.

            In case of the pendency of any receivership, insolvency,
liquidation, bankruptcy, reorganization, arrangement, adjustment, composition or
other judicial proceeding relative to the Company or any other obligor upon the
Notes or the property of the Company or of such other obligor or their
creditors, the Trustee (irrespective of whether the principal amount, Redemption
Price, Purchase Price, Fundamental Change Purchase Price, interest, Additional
Amounts or Additional Interest, if any, in respect of the Notes shall then be
due and payable as therein expressed or by declaration or otherwise and
irrespective of whether the Trustee shall have made any demand on the Company
for the payment of any such amount) shall be entitled and empowered, by
intervention in such proceeding or otherwise:

            (a) to file and prove a claim for the whole amount of the principal,
Redemption Price, Purchase Price, Fundamental Change Purchase Price, interest,
Additional Amounts or Additional Interest, if any, and to file such other papers
or documents as may be necessary or advisable in order to have the claims of the
Trustee (including any claim for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel or

                                       51
<PAGE>

any other amounts due the Trustee under Section 9.7) and of the Holders allowed
in such judicial proceeding, and

            (b) to collect and receive any moneys or other property payable or
deliverable on any such claims and to distribute the same;

and any custodian, receiver, assignee, trustee, liquidator, sequestrator or
similar official in any such judicial proceeding is hereby authorized by each
Holder to make such payments to the Trustee and, in the event that the Trustee
shall consent to the making of such payments directly to the Holders, to pay the
Trustee any amount due it for the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, and any other
amounts due the Trustee under Section 9.7.

            Nothing contained herein shall be deemed to authorize the Trustee to
authorize or consent to or accept or adopt on behalf of any Holder any plan of
reorganization, arrangement, adjustment or composition affecting the Notes or
the rights of any Holder thereof, or to authorize the Trustee to vote in respect
of the claim of any Holder in any such proceeding.

      Section 8.10. Priorities.

            If the Trustee collects any money pursuant to this ARTICLE VIII, it
shall pay out the money in the following order:

            FIRST: to the Trustee for amounts due under Section 9.7;

            SECOND: to Holders for amounts due and unpaid on the Securities for
the principal amount, Redemption Price, Purchase Price, Fundamental Change
Purchase Price, interest, Additional Amounts or Additional Interest, if any, as
the case may be, ratably, without preference or priority of any kind, according
to such amounts due and payable on the Notes; and

            THIRD: the balance, if any, to the Company.

            The Trustee may fix a record date and payment date for any payment
to Holders pursuant to this Section 8.10. At least 10 days prior to such record
date, the Trustee shall mail to each Holder and the Company a notice that states
the record date, the payment date and the amount to be paid.

      Section 8.11. Undertaking for Costs.

            In any suit for the enforcement of any right or remedy under this
Indenture or in any suit against the Trustee for any action taken or omitted by
it as Trustee, a court in its discretion may require the filing by any party
litigant (other than the Trustee) in the suit of an undertaking to pay the costs
of the suit, and the court in its discretion may assess reasonable costs,
including reasonable attorneys' fees and expenses, against any party litigant in
the suit, having due regard to the merits and good faith of the claims or
defenses made by the party litigant. This Section 8.11 does not apply to a suit
by the Trustee, a suit by a Holder pursuant to Section 8.7 or a suit by Holders
of more than 10% in aggregate principal amount of the Notes at

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<PAGE>

the time outstanding. This Section 8.11 shall be in lieu of Section 315(e) of
the TIA and such Section 315(e) is hereby expressly excluded from this
Indenture, as permitted by the TIA.

                                   ARTICLE IX

                                    TRUSTEE

      Section 9.1. Duties of Trustee.

            (a) If an Event of Default has occurred and is continuing, the
Trustee shall exercise the rights and powers vested in it by this Indenture and
use the same degree of care and skill in its exercise of those rights and powers
as a prudent man would exercise or use under the circumstances in the conduct of
his own affairs.

            (b) Except during the continuance of an Event of Default:

            (i)   the Trustee need perform only those duties that are
      specifically set forth in this Indenture and no others; and

            (ii)  in the absence of bad faith on its part, the Trustee may
      conclusively rely, as to the truth of the statements and the correctness
      of the opinions expressed therein, upon certificates or opinions furnished
      to the Trustee and conforming to the requirements of this Indenture, but
      in the case of any such certificates or opinions which by any provision
      hereof are specifically required to be furnished to the Trustee, the
      Trustee shall examine the certificates and opinions to determine whether
      or not they conform to the requirements of this Indenture, but need not
      confirm or investigate the accuracy of mathematical calculations or other
      facts stated therein.

            This Section 9.1(b) shall be in lieu of Section 315(a) of the TIA
and such Section 315(a) is hereby expressly excluded from this Indenture, as
permitted by the TIA.

            (c) The Trustee may not be relieved from liability for its own
negligent action, its own negligent failure to act or its own willful
misconduct, except that:

            (i)   this clause (c) does not limit the effect of clause (b) of
      this Section 9.1;

            (ii)  the Trustee shall not be liable for any error of judgment made
      in good faith by a Responsible Officer unless it is proved that the
      Trustee was negligent in ascertaining the pertinent facts;

            (iii) the Trustee shall not be liable with respect to any action it
      takes or omits to take in good faith in accordance with a direction
      received by it pursuant to Section 8.5 relating to the time, method and
      place of conducting any proceeding for any remedy available to the
      Trustee, or exercising any trust or power conferred upon the Trustee,
      under this Indenture; and

                                       53
<PAGE>

            (iv)  The Trustee may refuse to perform any duty or exercise any
      right or power or extend or risk its own funds or otherwise incur any
      financial liability unless it receives indemnity reasonably satisfactory
      to it against any loss, liability or expense.

            (d) Every provision of this Indenture that in any way relates to the
Trustee is subject to paragraphs (a), (b) and (c) of this Section.

            (e) Money held by the Trustee in trust hereunder need not be
segregated from other funds except to the extent required by law. The Trustee
(acting in any capacity hereunder) shall be under no liability for interest on
any money received by it hereunder unless otherwise agreed in writing with the
Company.

            (f) The Trustee shall comply with the reporting requirements set
forth in Section 313 of the TIA.

      Section 9.2. Rights of Trustee.

            Subject to its duties and responsibilities under the TIA and this
Indenture,

            (a) the Trustee may conclusively rely and shall be protected in
acting or refraining from acting upon any resolution, certificate, statement,
instrument, opinion, report, notice, request, direction, consent, order, bond,
debenture, note, other evidence of indebtedness or other paper or document
(whether in its original or facsimile form) believed by it to be genuine and to
have been signed or presented by the proper party or parties;

            (b) whenever in the administration of this Indenture the Trustee
shall deem it desirable that a matter be proved or established prior to taking,
suffering or omitting any action hereunder, the Trustee (unless other evidence
be herein specifically prescribed) may, in the absence of bad faith on its part,
conclusively rely upon an Officers' Certificate;

            (c) the Trustee may execute any of the trusts or powers hereunder or
perform any duties hereunder either directly or by or through agents or
attorneys and the Trustee shall not be responsible for any misconduct or
negligence on the part of any agent or attorney appointed with due care by it
hereunder;

            (d) the Trustee shall not be liable for any action taken, suffered,
or omitted to be taken by it in good faith which it reasonably believes to be
authorized or within its rights or powers conferred under this Indenture;

            (e) the Trustee may consult with counsel selected by it and any
advice or Opinion of Counsel shall be full and complete authorization and
protection in respect of any action taken or suffered or omitted by it hereunder
in good faith and in reliance on such advice or Opinion of Counsel;

            (f) the Trustee shall be under no obligation to exercise any of the
rights or powers vested in it by this Indenture at the request, order or
direction of any of the Holders, pursuant to the provisions of this Indenture,
unless such Holders shall have offered to the Trustee security or

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<PAGE>

indemnity satisfactory to it against the costs, expenses and liabilities which
may be incurred therein or thereby;

            (g) any request or direction of the Company mentioned herein shall
be sufficiently evidenced by a Company Request or Company Order and any
resolution of the Board of Directors may be sufficiently evidenced by a Board
Resolution;

            (h) the Trustee shall not be bound to make any investigation into
the facts or matters stated in any resolution, certificate, statement,
instrument, opinion, report, notice, request, direction, consent, order, bond,
debenture, note, other evidence of indebtedness or other paper or document, but
the Trustee, in its discretion, may make such further inquiry or investigation
into such facts or matters as it may see fit, and, if the Trustee shall
determine to make such further inquiry or investigation, it shall be entitled to
examine the books, records and premises of the Company, personally or by agent
or attorney at the sole cost of the Company and shall incur no liability or
additional liability of any kind by reason of such inquiry or investigation;

            (i) the Trustee shall not be deemed to have notice of any Default or
Event of Default unless a Responsible Officer of the Trustee has actual
knowledge thereof or unless written notice of any event which is in fact such a
default is received by the Trustee at the Corporate Trust Office of the Trustee,
and such notice references the Securities and this Indenture;

            (j) the rights, privileges, protections, immunities and benefits
given to the Trustee, including, without limitation, its right to be
indemnified, are extended to, and shall be enforceable by, the Trustee in each
of its capacities hereunder, and to each agent, custodian and other person
employed to act hereunder; and

            (k) the Trustee may request that the Company deliver an Officers'
Certificate setting forth the names of individuals and/or titles of officers
authorized at such time to take specified actions pursuant to this Indenture,
which Officers' Certificate may be signed by any person authorized to sign an
Officers' Certificate, including any person specified as so authorized in any
such certificate previously delivered and not superseded.

            (l) to the extent not prohibited by the TIA, in no event shall the
Trustee be responsible or liable for special , indirect, or consequential loss
or damage of any kind whatsoever (including, but not limited to, loss of profit)
irrespective of whether the Trustee has been advised of the likelihood of such
loss or damage and regardless of the form of action.

      Section 9.3. Individual Rights of Trustee.

            The Trustee in its individual or any other capacity may become the
owner or pledgee of Securities and may otherwise deal with the Company or its
Affiliates with the same rights it would have if it were not Trustee; provided
that the Trustee must comply with Section 9.10 and Section 9.11. Any Paying
Agent, Registrar, Conversion Agent or co-registrar may do the same with like
rights.

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<PAGE>

      Section 9.4. Trustee's Disclaimer.

            The Trustee makes no representation as to the validity or adequacy
of this Indenture or the Securities, it shall not be accountable for the
Company's use or application of the proceeds from the Securities, it shall not
be responsible for any statement in any registration statement for the
Securities under the Securities Act or in any offering document for the
Securities, this Indenture or the Securities (other than its certificate of
authentication), or the determination as to which beneficial owners are entitled
to receive any notices hereunder.

      Section 9.5. Notice of Defaults.

            If a Default occurs and if it is known to the Trustee, the Trustee
shall give to each Holder notice of the Default within 90 days after it occurs
or, if later, within 15 days after it is known to the Trustee, unless such
Default shall have been cured or waived before the giving of such notice.
Notwithstanding the preceding sentence, except in the case of a Default
described in Section 8.1(a), Section 8.1(b), Section 8.1(d) or Section 8.1(f),
the Trustee may withhold the notice if and so long as a committee of its
Responsible Officers in good faith determines that withholding the notice is in
the interests of the Holders. The preceding sentence shall be in lieu of the
proviso to Section 315(b) of the TIA and such proviso is hereby expressly
excluded from this Indenture, as permitted by the TIA.

      Section 9.6. Reports by Trustee to Holders.

            Within 60 days after each May 15 beginning with the May 15 following
the date of this Indenture, the Trustee shall mail to each Holder a brief report
dated as of such May 15 that complies with TIA Section 313(a), if required by
such Section 313(a). The Trustee also shall comply with TIA Section 313(b).

            Commencing at the time that this Indenture is qualified under the
TIA, a copy of each report at the time of its mailing to Holders shall be filed
with the SEC and each securities exchange, if any, on which the Securities are
listed. The Company agrees to notify the Trustee promptly whenever this
Indenture is qualified under the TIA and the Securities become listed on any
securities exchange and of any delisting thereof.

      Section 9.7. Compensation and Indemnity.

            The Company agrees to:

            (a) pay to the Trustee from time to time such compensation as the
Company and the Trustee shall from time to time agree in writing for all
services rendered by it hereunder (which compensation shall not be limited (to
the extent permitted by law) by any provision of law in regard to the
compensation of a trustee of an express trust);

            (b) reimburse the Trustee upon its request for all expenses,
disbursements and advances incurred or made by the Trustee in accordance with
any provision of this Indenture (including the compensation and the reasonable
expenses, advances and disbursements of its agents and counsel), except any such
expense, disbursement or advance as may be attributable to its own negligence or
willful misconduct; and

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<PAGE>

            (c) fully indemnify the Trustee or any predecessor Trustee and their
agents for, and to hold them harmless against, any and all loss, damage, claim,
liability, cost or expense (including attorney's fees and expenses, and taxes
(other than taxes based upon, measured by or determined by the income of the
Trustee)) incurred without negligent action, negligent failure to act or willful
misconduct on their part, arising out of or in connection with the acceptance or
administration of this trust, including the costs and expenses of defending
themselves against any claim (whether asserted by the Company or any Holder or
any other person) or liability in connection with the exercise or performance of
any of the Trustee's powers or duties hereunder, or in connection with enforcing
the provisions of this Section 9.7.

            With regard to its indemnification rights under Section 9.7(c) where
the Company has assumed the defense in any action or proceeding, the Trustee
shall have the right to employ separate counsel in any such action or proceeding
and participate in the investigation and defense thereof, and the Company shall
pay the reasonable fees and expenses of such separate counsel; provided,
however, that the Trustee may only employ separate counsel at the expense of the
Company if in the reasonable judgment of the Trustee (i) a conflict of interest
exists by reason of common representation or (ii) there are legal defenses
available to the Trustee that are different from or are in addition to those
available to the Company or if all parties commonly represented do not agree as
to the action (or inaction) of counsel.

            To secure the Company's payment obligations in this Section 9.7, the
Trustee shall have a lien prior to the Securities on all money or property held
or collected by the Trustee, except that held in trust to pay the principal
amount, Redemption Price, Purchase Price, Fundamental Change Purchase Price,
interest, Additional Amounts or Additional Interest, if any, as the case may be,
on particular Securities.

            The Company's payment obligations pursuant to this Section 9.7 shall
survive the discharge of this Indenture and the resignation or removal of the
Trustee. When the Trustee incurs expenses after the occurrence of a Default
specified in Section 8.1(j) or Section 8.1(k), the expenses including the
reasonable charges and expenses of its counsel, are intended to constitute
expenses of administration under any Bankruptcy Law.

      Section 9.8. Replacement of Trustee.

            The Trustee may resign by so notifying the Company; provided,
however, that no such resignation shall be effective until a successor Trustee
has accepted its appointment pursuant to this Section 9.8. The Holders of a
majority in aggregate principal amount of the Securities at the time outstanding
may remove the Trustee by so notifying the Trustee and the Company. The Company
shall remove the Trustee if:

            (a) the Trustee fails to comply with Section 9.10;

            (b) the Trustee is adjudged bankrupt or insolvent;

            (c) a receiver or public officer takes charge of the Trustee or its
property; or

            (d) the Trustee otherwise becomes incapable of acting.

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<PAGE>

            If the Trustee resigns or is removed or if a vacancy exists in the
office of Trustee for any reason, the Company shall promptly appoint, by Board
Resolution, a successor Trustee.

            A successor Trustee shall deliver a written acceptance of its
appointment to the retiring Trustee and to the Company satisfactory in form and
substance to the retiring Trustee and the Company. Thereupon the resignation or
removal of the retiring Trustee shall become effective, and the successor
Trustee shall have all the rights, powers and duties of the Trustee under this
Indenture. The successor Trustee shall mail a notice of its succession to
Holders. The retiring Trustee shall promptly transfer all property held by it as
Trustee to the successor Trustee, upon payment of all the retiring Trustee's
fees and expenses then due and payable and subject to the lien provided for in
Section 9.7.

            If a successor Trustee does not take office within 30 days after the
retiring Trustee resigns or is removed, the retiring Trustee, the Company or the
Holders of a majority in aggregate principal amount of the Securities at the
time outstanding may petition any court of competent jurisdiction at the expense
of the Company for the appointment of a successor Trustee.

            If the Trustee fails to comply with Section 9.10, any Holder may
petition any court of competent jurisdiction for the removal of the Trustee and
the appointment of a successor Trustee.

      Section 9.9. Successor Trustee by Merger.

            If the Trustee consolidates with, merges or converts into, or
transfers all or substantially all its corporate trust business or assets to,
another corporation, the resulting, surviving or transferee corporation without
any further act shall be the successor Trustee. As soon as practicable, the
successor Trustee shall mail a notice of its succession to the Company and the
Holders. Any such successor must nevertheless be eligible and qualified under
the provisions of Section 9.10 hereof.

      Section 9.10. Eligibility; Disqualification.

            The Trustee and any successor Trustee shall at all times satisfy the
requirements of TIA Sections 310(a)(1) and 310(b) ; provided, however, that
there shall be excluded from the operation of TIA Section 310(b)(1) any
indenture or indentures under which other securities, or certificates of
interest or participation in other securities, of the Company are outstanding,
if the requirements for such exclusion set forth in TIA Section 310(b)(1) are
met. Nothing contained herein shall prevent the Trustee from filing with the SEC
the application referred to in the penultimate paragraph of TIA Section 310(b).

            The Trustee (or its parent holding company) shall have a combined
capital and surplus of at least $50,000,000 as set forth in its most recent
published annual report of condition.

            If at any time the Trustee shall cease to be eligible in accordance
with the provisions of this Section 9.10, it shall resign immediately in the
manner and with the effect specified in this ARTICLE IX.

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<PAGE>

      Section 9.11. Preferential Collection of Claims Against Company.

            The Trustee shall comply with TIA Section 311(a), excluding any
creditor relationship listed in TIA Section 311(b). A Trustee who has resigned
or been removed shall be subject to TIA Section 311(a) to the extent indicated
therein.

                                   ARTICLE X

                             DISCHARGE OF INDENTURE

      Section 10.1. Discharge of Liability on Securities.

            When (i) the Company delivers to the Trustee all outstanding
Securities (other than Securities replaced or repaid pursuant to Section 2.7)
for cancellation or (ii) all outstanding Securities have become due and payable
(whether at the Stated Maturity or upon acceleration, or on any Redemption Date,
Purchase Date or Fundamental Change Purchase Date, or upon conversion) and the
Company irrevocably deposits with the Paying Agent or Conversion Agent cash or
securities (as applicable under the terms of this Indenture) sufficient to pay
all amounts due and owing on all outstanding Securities (other than Securities
replaced pursuant to Section 2.7), and if in either case the Company pays all
other sums payable hereunder by the Company, then this Indenture shall, subject
to Section 9.7, cease to be of further effect, subject to any extension required
by Section 12.13 to effect settlement upon conversion of the Notes. The Trustee
shall join in the execution of a document prepared by the Company acknowledging
satisfaction and discharge of this Indenture on demand of the Company
accompanied by an Officers' Certificate and Opinion of Counsel and at the cost
and expense of the Company.

      Section 10.2. Repayment to the Company.

            The Trustee, the Paying Agent and the Conversion Agent shall return
to the Company upon written request any cash or securities held by them for the
payment of any amount with respect to the Securities that remains unclaimed for
two years, subject to applicable unclaimed property law. After return to the
Company, Holders entitled to the cash or securities must look to the Company for
payment as general creditors unless an applicable abandoned property law
designates another person and the Trustee, the Paying Agent and the Conversion
Agent shall have no further liability to the Holders with respect to such cash
or securities for that period commencing after the return thereof.

                                   ARTICLE XI

                                   AMENDMENTS

      Section 11.1. Without Consent of Holders of Notes.

            The Company and the Trustee may amend this Indenture or the
Securities without the consent of any Holder to:

            (a) add to the covenants of the Company for the benefit of the
Holders of Securities;

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<PAGE>

            (b) surrender any right or power herein conferred upon the Company;

            (c) provide for conversion rights of Holders of Notes if any
reclassification or change of the Common Stock or any consolidation, merger or
disposition of all or substantially all of the Company's properties and assets
occurs;

            (d) provide for the assumption of the Company's obligations to the
Holders of Notes in the case of a merger, consolidation, conveyance, transfer,
sale, lease or other disposition pursuant to ARTICLE VII;

            (e) increase the Conversion Rate; provided, however, that such
increase in the Conversion Rate shall not adversely affect the interests of the
Holders of Notes (after taking into account tax and other consequences of such
increase);

            (f) comply with the requirements of the SEC in order to effect or
maintain the qualification of this Indenture under the TIA;

            (g) make any changes or modifications necessary in connection with
the registration of the Securities under the Securities Act as contemplated in
the Registration Rights Agreement; provided, however, that such action pursuant
to this clause (g) does not, in the good faith opinion of the Board of Directors
(as evidenced by a Board Resolution), adversely affect the interests of the
Holders of Securities in any material respect;

            (h) cure any ambiguity, correct or supplement any provision herein
which may be inconsistent with any other provision herein or which is otherwise
defective, or to make any other provisions with respect to matters or questions
arising under this Indenture which the Company may deem necessary or desirable
and which shall not be inconsistent with the provisions of this Indenture;
provided, however, that such action pursuant to this clause (h) does not, in the
good faith opinion of the Board of Directors (as evidenced by a Board
Resolution), adversely affect the interests of the Holders of Securities in any
material respect;

            (i) to evidence the succession of another Person to the Company or
any other obligor upon the Notes, and the assumption by any such successor of
the covenants of the Company or such obligor herein and in the Notes, in each
case in compliance with the provisions of this Indenture;

            (j) to evidence and provide the acceptance of the appointment of a
successor trustee hereunder; or

            (k) to require the Company to settle (i) its obligation to purchase
Notes under ARTICLE IV in cash or (ii) its Conversion Obligation in cash with
respect to the principal amount of Notes surrendered for conversion.

      Section 11.2. With Consent of Holders of Notes.

            Except as provided below in this Section 11.2, this Indenture or the
Securities may be amended, and noncompliance in any particular instance with any
provision of this

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<PAGE>

Indenture or the Securities may be waived, in each case with the consent or
affirmative vote of the Holders of at least a majority of the principal amount
of the Notes at the time outstanding.

            Without the consent or the affirmative vote of each Holder of Notes
affected thereby (in addition to the consent or the affirmative vote of the
Holders of at least a majority of the principal amount of the Securities at the
time outstanding), an amendment or waiver under this Section 11.2 may not:

            (a) change the maturity of the principal amount of, or the payment
date of any installment of interest, Additional Amounts or Additional Interest,
if any, on, any Security;

            (b) reduce the principal amount of, or interest, Additional Amounts
or Additional Interest, if any, on, or the Redemption Price, Purchase Price or
Fundamental Change Purchase Price of, any Note;

            (c) change the currency of payment of principal amount of, or
interest, Additional Amounts or Additional Interest, if any, on, or the
Redemption Price, Purchase Price or Fundamental Change Purchase Price of, any
Note from U.S. Dollars;

            (d) impair or adversely affect the manner of calculation or rate of
accrual of interest, Additional Amounts or Additional Interest, if any, on any
Note;

            (e) impair the right of any Holder to institute suit for the
enforcement of any payment or with respect to, or conversion of, any Note;

            (f) modify the Company's obligation to maintain a Registrar, Paying
Agent, Conversion Agent and an office or agency where notices and demands to or
upon the Company in respect of the Securities and this Indenture may be served
in the Borough of Manhattan, New York City;

            (g) impair or adversely affect the conversion rights of the Holders
of the Notes as provided in ARTICLE XII;

            (h) impair or adversely affect the purchase rights of the Holders of
the Notes as provided in ARTICLE IV or ARTICLE V;

            (i) modify the redemption provisions of ARTICLE III in a manner
adverse to the Holders of Notes;

            (j) reduce the percentage of the principal amount of the outstanding
Notes the consent or affirmative vote of whose Holders is required for any such
amendment;

            (k) reduce the percentage of the principal amount of the outstanding
Notes the consent or affirmative vote of whose Holders is required for any
waiver of any past Default provided for in this Indenture; or

            (l) waive any matter set forth in Section 8.4(a), Section 8.4(b), or
Section 8.4(c).

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<PAGE>

            It shall not be necessary for the consent of the Holders under this
Section 11.2 to approve the particular form of any proposed amendment, but it
shall be sufficient if such consent approves the substance thereof.

            After an amendment under this Section 11.2 becomes effective, the
Company shall mail to each Holder a notice briefly describing the amendment.

      Section 11.3. Compliance with Trust Indenture Act.

            Every supplemental indenture executed pursuant to this Article shall
comply with the TIA.

      Section 11.4. Revocation and Effect of Consents, Waivers and Actions.

            Until an amendment, waiver or other action by Holders becomes
effective, a consent thereto by a Holder of a Note hereunder is a continuing
consent by the Holder and every subsequent Holder of that Security or portion of
the Note that evidences the same obligation as the consenting Holder's Note,
even if notation of the consent, waiver or action is not made on the Note.
However, any such Holder or subsequent Holder may revoke the consent, waiver or
action as to such Holder's Note or portion of the Note if the Trustee receives
the notice of revocation before the date the amendment, waiver or action becomes
effective. After an amendment, waiver or action becomes effective, it shall bind
every Holder.

      Section 11.5. Notation on or Exchange of Securities.

            Securities authenticated and delivered after the execution of any
supplemental indenture pursuant to this ARTICLE XI may, and shall if required by
the Trustee, bear a notation in form approved by the Trustee as to any matter
provided for in such supplemental indenture. If the Company shall so determine,
new Securities so modified as to conform, in the opinion of the Trustee and the
Board of Directors, to any such supplemental indenture may be prepared and
executed by the Company and authenticated and delivered by the Trustee in
exchange for outstanding Securities.

      Section 11.6. Trustee to Sign Supplemental Indentures.

            The Trustee shall sign any supplemental indenture authorized
pursuant to this ARTICLE XI if the amendment contained therein does not
adversely affect the rights, duties, liabilities or immunities of the Trustee.
If it does, the Trustee may, but need not, sign such supplemental indenture. In
signing such supplemental indenture the Trustee shall receive, and (subject to
the provisions of Section 9.1) shall be fully protected in relying upon, an
Officers' Certificate and an Opinion of Counsel stating that such amendment is
authorized or permitted by this Indenture.

      Section 11.7. Effect of Supplemental Indentures.

            Upon the execution of any supplemental indenture under this Article,
this Indenture shall be modified in accordance therewith, and such supplemental
indenture shall form

                                       62
<PAGE>

a part of this Indenture for all purposes; and every Holder of Securities
theretofore or thereafter authenticated and delivered hereunder shall be bound
thereby.

                                  ARTICLE XII

                                   CONVERSION

      Section 12.1. Conversion Right.

            (a) Subject to and upon compliance with the provisions of this
ARTICLE XII, a Holder of a Note shall have the right, at such Holder's option,
to convert all or any portion (if the portion to be converted is $1,000 of the
principal amount or an integral multiple thereof) of such Note into, subject to
Section 12.13 and the provisions of this Section 12.1, a number of shares of
Common Stock equal to the product of (x) the Conversion Rate in effect on the
date of conversion times (y) the quotient of the principal amount of the Note or
portion thereof surrendered for conversion divided by 1,000:

            (i)   during any Conversion Period if, on each of at least 20
      Trading Days in the period of 30 consecutive Trading Days ending on the
      first Trading Day of the Conversion Period, the Closing Sale Price of the
      Common Stock exceeded 120% of the Conversion Price in effect on the 30th
      Trading Day of such period of 30 consecutive Trading Days;

            (ii)  at any time prior to 5:00 p.m., New York City time, on the
      second Business Day preceding the Redemption Date , if such Note has been
      called for redemption pursuant to ARTICLE III; or

            (iii) as provided in clause (b) of this Section 12.1.

            The Conversion Agent shall, on behalf of the Company, determine on
the first Trading Day of each Conversion Period whether the Notes shall be
convertible as a result of the occurrence of an event specified in clause (a)(i)
above and, if the Notes shall be so convertible, the Conversion Agent shall
promptly deliver to the Company and the Trustee notice thereof, and thereupon
the Company shall promptly make Public Notice to the Holders thereof. Any notice
so given shall be conclusively presumed to have been duly given, whether or not
the Holder receives such notice.

            Notes called for redemption may be converted at any time on and
after the date that the Company gives notice to the Holders of such right until
5:00 p.m., New York City time, on the second Business Day preceding the
corresponding Redemption Date.

            With respect to any conversion of a Note during a Registration
Default Period following satisfaction of any of the conditions to conversion
described in clauses (a)(i)-(a)(iii) above (and during the prescribed time
periods in respect thereof), a Holder shall be entitled, subject to Section
12.13, to 103% of the number of shares of Common Stock that the Holder would
have otherwise been entitled to upon conversion in respect of the portion of the
Conversion Obligation that the Company settles in Common Stock.

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<PAGE>

            (b) (i) In the event that:

                  (A)   the Company distributes to all holders of the Common
            Stock rights or warrants entitling them (for a period expiring
            within 60 days of the Record Date for such distribution) to
            subscribe for or purchase Common Stock at a price per share of
            Common Stock less than the Closing Sale Price of the Common Stock on
            the Business Day immediately preceding the public announcement of
            such distribution;

                  (B)   the Company distributes to all holders of its Common
            Stock cash or other assets, debt securities or rights or warrants to
            purchase its securities, including the declaration of any cash
            dividends, payable quarterly or otherwise, where the Fair Market
            Value (as determined by the Board of Directors) of such distribution
            per share of Common Stock exceeds 10% of the Closing Sale Price of
            the Common Stock on the Business Day immediately preceding the date
            of declaration of such distribution; or

                  (C)   a Fundamental Change occurs,

then, in each case, the Notes may be surrendered for conversion at any time on
and after the date that the Company gives notice (including by making a Public
Notice) to the Holders of such right, which shall be, in the case of (A) or (B),
not less than 20 Business Days prior to the Ex-Dividend Time for such
distribution, or, in the case of (C), within 20 Business Days after the
occurrence of the Fundamental Change, until 5:00 p.m., New York City time, on
the earlier of the Business Day immediately preceding the Ex-Dividend Time or
the date the Company announces that such distribution shall not take place in
the case of (A) or (B), or within 20 Business Days of the Company's delivery of
the notice of the Fundamental Change in the case of (C); provided, however, that
in the case of (A) or (B), a Holder of Notes may not surrender Notes for
conversion if the Holder shall otherwise participate in such distribution
without conversion.

            (ii)  In addition, in the event that the Company consolidates or
      merges with or into another Person, or is a party to a binding share
      exchange pursuant to which the Common Stock would be converted into cash,
      securities or other property as set forth in Section 12.4, then the Notes
      may be surrendered for conversion at any time from and after the date
      which is 15 calendar days prior to the date the Company announces by
      Public Notice as the anticipated effective time of such transaction until
      15 calendar days after the actual date of such transaction.

            (c)   Notwithstanding the foregoing, a Note in respect of which a
Holder has delivered a Purchase Notice or a Fundamental Change Purchase Notice,
as the case may be, exercising such Holder's right to require the Company to
repurchase such Note may be converted only if such Purchase Notice or
Fundamental Change Purchase Notice is withdrawn in accordance with Section
4.2(b) or Section 5.2(b) prior to 5:00 p.m., New York City time, on the Business
Day immediately preceding such Purchase Date or Fundamental Change Purchase
Date.

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      Section 12.2. Conversion Procedures; Conversion Rate; Fractional Shares.

            (a) Subject to Section 12.13, each Note shall be convertible at the
office of the Conversion Agent into fully paid and nonassessable shares of
Common Stock (calculated to the nearest 1/10,000th of a share).

            On the first date the Notes become convertible under the
circumstances described in Section 12.1, the Company shall make an election (the
"PRINCIPAL CONVERSION SETTLEMENT ELECTION") and notify the Holders in writing
whether a Holder who surrenders a Note (each, a "SURRENDERED SECURITY") will be
entitled to receive, in respect of the principal amount of such Note upon
surrender thereof, 100% Common Stock, 100% cash or a combination of cash and
Common Stock. If the Company elects to settle the Conversion Obligation relating
to the principal amount of such Note in a combination of cash and Common Stock,
the Company shall specify the percentage of the principal amount to be satisfied
in cash. This notification, once provided to a Holder on the date the Notes
first become convertible, is irrevocable and legally binding with regard to any
conversion of the Notes under the circumstances described in Section 12.1.

            The Conversion Agent shall notify the Company when it receives a
Conversion Notice. Settlement of the conversion obligation relating to the
principal amount of any Surrendered Securities shall be in accordance with the
allocation set forth in the Principal Conversion Settlement Election. The
Company shall determine the Excess Amount, and shall set forth the method for
settling the Conversion Obligation in respect of the Excess Amount in accordance
with the procedure set forth in Section 12.13. If the Company elects to settle
in Common Stock only, a certificate for the number of full shares of Common
Stock into which the Notes are converted (and cash in lieu of fractional shares)
shall be delivered by the Company to such Holder, assuming all of the other
requirements have been satisfied by such Holder, as soon as practicable after
the Company issues its notification of its chosen method of settlement in
accordance with Section 12.13. If the Company elects to settle in cash or a
combination of cash and Common Stock, the cash and, if applicable, a certificate
for the number of full shares of Common Stock into which the Notes are converted
(and cash in lieu of fractional shares) shall be paid and delivered to such
Holder, assuming all of the other requirements have been satisfied by such
Holder, in accordance with Section 12.13. Notwithstanding the foregoing, the
Company shall not be required to deliver certificates for Common Stock while the
stock transfer books for such stock or the security register are duly closed for
any purpose, but certificates for Common Stock shall be issued and delivered as
soon as practicable after the opening of such books or security register.

            Except as described in Section 12.9, the Company will not make any
payment in cash or Common Stock or other adjustment for accrued and unpaid
interest, Additional Amounts or Additional Interest on any Notes when they are
converted. The Company's delivery to the Holder of the full number of shares of
Common Stock into which the Note is convertible (or, at the Company's option,
cash, or a combination of cash and Common Stock, in lieu thereof as provided in
Section 12.13), together with any cash payment for such Holder's fractional
shares, shall be deemed to satisfy the Company's obligation to pay the principal
amount of the Note and to satisfy its obligation to pay accrued and unpaid
interest, Additional Amounts and Additional Interest, if any through the
conversion date. As a result, accrued interest, Additional Amounts

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<PAGE>

and Additional Interest are deemed paid in full rather than cancelled,
extinguished or forfeited. Notwithstanding the foregoing, accrued interest,
Additional Amounts and Additional Interest, if any, will be payable in cash upon
any conversion of Notes made concurrently with or after acceleration of the
Notes following an Event of Default.

            If a Holder has exercised its right to require the Company to
purchase its Notes pursuant to ARTICLE IV or ARTICLE V, such Holder's conversion
rights on the Notes so subject to purchase shall expire at 5:00 p.m., New York
City time, on the Business Day immediately preceding the Purchase Date or
Fundamental Change Purchase Date, as the case may be, unless the Company shall
default in its payment obligation to such Holder. Notwithstanding the foregoing,
a Note in respect of which a Holder has delivered a Purchase Notice or a
Fundamental Change Purchase Notice, as the case may be, exercising such Holder's
right to require the Company to purchase such Note may be converted only if such
Purchase Notice or Fundamental Change Purchase Notice is withdrawn in accordance
with Section 4.2(b) or Section 5.2(b) prior to 5:00 p.m., New York City time, on
the Business Day immediately preceding such Purchase Date or Fundamental Change
Purchase Date.

            (b) Before any Holder shall be entitled to convert any Notes into
Common Stock, such Holder shall, in the case of Global Securities, comply with
the Applicable Procedures of the Depositary in effect at that time, and in the
case of Certificated Securities, surrender such Securities, duly endorsed to the
Company or in blank if required by the Conversion Agent, at the office of the
Conversion Agent, and shall give written notice to the Company at said office or
place in the form of the Conversion Notice attached to the Note (the "CONVERSION
Notice") that such Holder elects to convert the same and shall state in writing
therein the principal amount of Notes to be converted (in whole or in part so
long as the principal amount to be converted is in multiples of $1,000) and the
name or names (with addresses) in which such Holder wishes the certificate or
certificates for Common Stock to be issued.

            Before any such conversion, a Holder also shall pay all funds
required, if any, relating to interest, Additional Amounts or Additional
Interest, if any, on the Notes, as provided in Section 12.9, and all taxes or
duties, if any, as provided in Section 12.8.

            If more than one Note shall be surrendered for conversion at one
time by the same Holder, the number of full shares of Common Stock that shall be
deliverable upon conversion shall be computed on the basis of the aggregate
principal amount of the Notes (or specified portions thereof to the extent
permitted thereby) so surrendered.

            If shares of Common Stock to be issued upon conversion of a
Restricted Security are to be issued in the name of a Person other than the
Holder of such Restricted Security, such Holder shall deliver to the Conversion
Agent a certification in substantially the form set forth in a Transfer
Certificate dated the date of surrender of such Restricted Security and signed
by such Holder, as to compliance with the restrictions on transfer applicable to
such Restricted Security. The Company shall not be required to issue Common
Stock upon conversion of any such Restricted Security to a Person other than the
Holder if such Restricted Security is not so accompanied by a properly completed
certification, and the Registrar shall not be required to register Common Stock
upon conversion of any such Restricted Security in the name of a Person

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<PAGE>

other than the Holder if such Restricted Security is not so accompanied by a
properly completed certification.

            (c) A Note shall be deemed to have been converted immediately prior
to 5:00 p.m., New York City time, on the date on which all of the conversion
requirements set forth in Section 12.2(b) have been satisfied, and the person or
persons entitled to receive the Common Stock issuable upon such conversion shall
be treated for all purposes as the record Holder or Holders of such Common Stock
as of 5:00 p.m., New York City time, on such date

            (d) In case any Certificated Security shall be surrendered for
partial conversion, the Company shall execute and the Trustee shall authenticate
and deliver to or upon the written order of the Holder of the Security so
surrendered, without charge to such Holder (subject to the provisions of Section
12.8), a new Note or Notes in authorized denominations in an aggregate principal
amount equal to the unconverted portion of the surrendered Certificated
Securities.

      Section 12.3. Adjustment of Conversion Rate.

            The Conversion Rate shall be adjusted from time to time as follows:

            (a) In case the Company shall, at any time or from time to time
after the initial Issue Date while any of the Notes are outstanding, pay a
dividend or make a distribution in Common Stock to all or substantially all
holders of its outstanding Common Stock, then the Conversion Rate in effect
immediately prior to the close of business on the Record Date fixed for the
determination of stockholders entitled to receive such dividend or other
distribution shall be increased so that the Holder of any Note thereafter
surrendered for conversion shall be entitled to receive that number of shares of
Common Stock which it would have received had such Note been converted
immediately prior to the happening of such event as well as such additional
shares it would have received as a result of such event. Such increase shall
become effective immediately prior to the opening of business on the day
following the Record Date fixed for such determination. If any dividend or
distribution of the type described in this Section 12.3(a) is declared but not
so paid or made, the Conversion Rate shall again be adjusted to the Conversion
Rate which would then be in effect if such dividend or distribution had not been
declared.

            (b) In case the Company shall, at any time or from time to time
after the initial Issue Date while any of the Notes are outstanding, subdivide
its outstanding shares of Common Stock into a greater number of Common Stock or
combine its outstanding shares of Common Stock into a smaller number of Common
Stock, then the Conversion Rate in effect immediately prior to the close of
business on the day upon which such subdivision or combination becomes effective
shall be adjusted so that the Holder of any Note thereafter surrendered for
conversion shall be entitled to receive that number of shares of Common Stock
which it would have received had such Note been converted immediately prior to
the happening of such event as well as such additional shares as it would have
received as a result of such event. Such adjustment shall become effective
immediately prior to the opening of business on the day following the day upon
which such subdivision or combination becomes effective.

            (c) In case the Company shall, at any time or from time to time
after the initial Issue Date while any of the Notes are outstanding, issue
rights or warrants for a period expiring

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<PAGE>

within 60 days (other than any rights or warrants referred to in Section
12.3(d)) to all or substantially all holders of its outstanding Common Stock
entitling them to subscribe for or purchase Common Stock (or securities
convertible into or exchangeable or exercisable for Common Stock), at a price
per share of Common Stock (or having a conversion, exchange or exercise price
per share of Common Stock) less than the Closing Sale Price of the Common Stock
on the Business Day immediately preceding the date of announcement of such
issuance (treating the conversion, exchange or exercise price per share of
Common Stock of the securities convertible, exchangeable or exercisable into
Common Stock as equal to (x) the sum of (i) the price for a unit of the security
convertible into or exchangeable or exercisable for Common Stock and (ii) any
additional consideration initially payable upon the conversion of or exchange or
exercise for such security into Common Stock divided by (y) the number of shares
of Common Stock initially underlying such convertible, exchangeable or
exercisable security), then the Conversion Rate shall be increased by
multiplying the Conversion Rate in effect at the opening of business on the date
after such date of announcement by a fraction:

            (i)   the numerator of which shall be the number of shares of Common
      Stock outstanding at the close of business on the date of announcement,
      plus the total number of additional shares of Common Stock so offered for
      subscription or purchase (or into which the convertible, exchangeable or
      exercisable securities so offered are convertible, exchangeable or
      exercisable); and

            (ii)  the denominator of which shall be the number of shares of
      Common Stock outstanding on the close of business on the date of
      announcement, plus the number of shares of Common Stock (or convertible,
      exchangeable or exercisable securities) which the aggregate offering price
      of the total number of shares of Common Stock (or convertible,
      exchangeable or exercisable securities) so offered for subscription or
      purchase (or the aggregate conversion, exchange or exercise price of the
      convertible, exchangeable or exercisable securities so offered) would
      purchase at such Closing Sale Price of the Common Stock.

            Such increase shall become effective immediately prior to the
opening of business on the day following the Record Date for such determination.
To the extent that shares of Common Stock (or securities convertible,
exchangeable or exercisable into shares of Common Stock) are not delivered
pursuant to such rights or warrants, upon the expiration or termination of such
rights or warrants, the Conversion Rate shall be readjusted to the Conversion
Rate which would then be in effect had the adjustments made upon the issuance of
such rights or warrants been made on the basis of the delivery of only the
number of shares of Common Stock (or securities convertible, exchangeable or
exercisable into shares of Common Stock) actually delivered. In the event that
such rights or warrants are not so issued, the Conversion Rate shall again be
adjusted to be the Conversion Rate which would then be in effect if the Record
Date fixed for the determination of stockholders entitled to receive such rights
or warrants had not been fixed. In determining whether any rights or warrants
entitle the holders to subscribe for or purchase shares of Common Stock at less
than such Closing Sale Price, and in determining the aggregate offering price of
such shares of Common Stock, there shall be taken into account any consideration
received for such rights or warrants, the value of such consideration if other
than cash, to be determined by the Board of Directors.

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<PAGE>

            (d) (A) In case the Company shall, at any time or from time to time
after the initial Issue Date while any of the Notes are outstanding, by dividend
or otherwise, distribute to all or substantially all holders of its outstanding
shares of Common Stock (including any such distribution made in connection with
a consolidation or merger in which the Company is the continuing corporation and
the shares of Common Stock are not changed or exchanged), shares of its capital
stock, evidences of its Indebtedness or other assets, including securities, but
excluding (i) dividends or distributions of Common Stock referred to in Section
12.3(a), (ii) any rights or warrants referred to in Section 12.3(c), (iii)
dividends and distributions paid exclusively in cash referred to in Section
12.3(e) and (iv) dividends and distributions of stock, securities or other
property or assets (including cash) in connection with the reclassification,
change, merger, consolidation, statutory share exchange, combination, sale or
conveyance to which Section 12.4 applies (such capital stock, evidence of its
indebtedness, other assets or securities being distributed hereinafter in this
Section 12.3(d) called the "DISTRIBUTED ASSETS"), then, in each such case,
subject to paragraphs (D) and (E) of this Section 12.3(d), the Conversion Rate
shall be increased by multiplying the Conversion Rate in effect immediately
prior to the close of business on the Record Date with respect to such
distribution by a fraction:

            (ii)  the numerator of which shall be the Current Market Price; and

            (iii) the denominator of which shall be such Current Market Price of
      the Common Stock, less the Fair Market Value on such date of the portion
      of the distributed assets so distributed applicable to one share of Common
      Stock (determined on the basis of the number of shares of Common Stock
      outstanding on the Record Date) on such date.

            Such increase shall become effective immediately prior to the
opening of business on the day following the Record Date for such distribution.
In the event that such dividend or distribution is not so paid or made, the
Conversion Rate shall again be adjusted to be the Conversion Rate which would
then be in effect if such dividend or distribution had not been declared.

            (B)   If the Board of Directors determines the Fair Market Value of
any distribution for purposes of this Section 12.3(d) by reference to the actual
or when issued trading market for any distributed assets comprising all or part
of such distribution, it must in doing so consider the prices in such market
over the same period (the "REFERENCE PERIOD") used in computing the Current
Market Price pursuant to Section 12.3(g) below to the extent possible, unless
the Board of Directors determines in good faith that determining the Fair Market
Value during the Reference Period would not be in the best interests of the
Holders.

            (C)   In the event any such distribution consists of shares of
capital stock of, or similar Equity Interests in, one or more of the Company's
Subsidiaries (a "SPIN-OFF"), the Fair Market Value of the securities to be
distributed shall equal the average of the Closing Sale Prices of such
securities on the principal securities market on which such securities are
traded for the five consecutive Trading Days commencing on and including the
sixth Trading Day of those securities after the effectiveness of the Spin-Off,
and the Current Market Price shall be measured for the same period. In the
event, however, that an underwritten initial public offering of the securities
in the Spin-Off occurs simultaneously with the Spin-Off, Fair Market Value of
the securities distributed in the Spin-Off shall mean the initial public
offering price of such securities

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<PAGE>

and the Current Market Price shall mean the Closing Sale Price for the Common
Stock on the same Trading Day.

            (D)   Rights or warrants distributed by the Company to all holders
of the outstanding shares of Common Stock entitling them to subscribe for or
purchase Equity Interests of the Company (either initially or under certain
circumstances), which rights or warrants, until the occurrence of a specified
event or events ("TRIGGER EVENT"), (x) are deemed to be transferred with such
shares of Common Stock, (y) are not exercisable and (z) are also issued in
respect of future issuances of shares of Common Stock shall be deemed not to
have been distributed for purposes of this Section 12.3(d) (and no adjustment to
the Conversion Rate under this Section 12.3(d) shall be required) until the
occurrence of the earliest Trigger Event. If such right or warrant is subject to
subsequent events, upon the occurrence of which such right or warrant shall
become exercisable to purchase different distributed assets, evidences of
indebtedness or other assets, or entitle the holder to purchase a different
number or amount of the foregoing or to purchase any of the foregoing at a
different purchase price, then the occurrence of each such event shall be deemed
to be the date of issuance and Record Date with respect to a new right or
warrant (and a termination or expiration of the existing right or warrant
without exercise by the holder thereof). In addition, in the event of any
distribution (or deemed distribution) of rights or warrants, or any Trigger
Event or other event (of the type described in the preceding sentence) with
respect thereto, that resulted in an adjustment to the Conversion Rate under
this Section 12.3(d):

            (i)   in the case of any such rights or warrants which shall all
      have been redeemed or repurchased without exercise by any holders thereof,
      the Conversion Rate shall be readjusted upon such final redemption or
      repurchase to give effect to such distribution or Trigger Event, as the
      case may be, as though it were a cash distribution, equal to the per share
      redemption or repurchase price received by a holder of shares of Common
      Stock with respect to such rights or warrants (assuming such holder had
      retained such rights or warrants), made to all holders of Common Stock as
      of the date of such redemption or repurchase; and

            (ii)  in the case of such rights or warrants which shall have
      expired or been terminated or redeemed without exercise, the Conversion
      Rate shall be readjusted as if such rights and warrants had never been
      issued.

            (E)   For purposes of this Section 12.3(d) and Section 12.3(a),
Section 12.3(b) and Section 12.3(c), any dividend or distribution to which this
Section 12.3(d) is applicable that also includes (x) shares of Common Stock, (y)
a subdivision or combination of shares of Common Stock to which Section 12.3(b)
applies or (z) rights or warrants to subscribe for or purchase shares of Common
Stock to which Section 12.3(c) applies (or any combination thereof), shall be
deemed instead to be:

            (i)   a dividend or distribution of the evidences of indebtedness,
      assets, shares of capital stock, rights or warrants, other than such
      shares of Common Stock, such subdivision or combination or such rights or
      warrants to which Section 12.3(a), Section 12.3(b) and Section 12.3(c)
      apply, respectively (and any Conversion Rate adjustment

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<PAGE>

      required by this Section 12.3(d) with respect to such dividend or
      distribution shall then be made), immediately followed by

            (ii)  a dividend or distribution of such shares of Common Stock,
      such subdivision or combination or such rights or warrants (and any
      further Conversion Rate increase required by Section 12.3(a), Section
      12.3(b) and Section 12.3(c) with respect to such dividend or distribution
      shall then be made), except:

                        (1)   the Record Date of such dividend or distribution
                  shall be substituted as (i) "the date fixed for the
                  determination of stockholders entitled to receive such
                  dividend or other distribution," "Record Date fixed for such
                  determinations" and "Record Date" within the meaning of
                  Section 12.3(a), (ii) "the day upon which such subdivision or
                  combination becomes effective" within the meaning of Section
                  12.3(b), and (iii) as "the Record Date fixed for the
                  determination of the stockholders entitled to receive such
                  rights or warrants" and such "Record Date" within the meaning
                  of Section 12.3(c); and

                        (2)   any reduction or increase in the number of shares
                  of Common Stock resulting from such subdivision or combination
                  shall be disregarded in connection with such dividend or
                  distribution.

            (e)   In case the Company shall, at any time or from time to time
after the initial Issue Date while any of the Notes are outstanding, by dividend
or otherwise, distribute to all or substantially all holders of its outstanding
shares of Common Stock, cash (including any quarterly cash dividends, but
excluding any cash that is distributed upon a reclassification, change, merger,
consolidation, statutory share exchange, combination, sale or conveyance to
which Section 12.4 applies or as part of a distribution referred to in Section
12.3(d)), then, and in each case, immediately after the close of business on
such date, the Conversion Rate shall be increased by multiplying the Conversion
Rate in effect immediately prior to the close of business of such Record Date by
a fraction:

                  (A)   the numerator of which shall be equal to the Current
            Market Price on such date; and

                  (B)   the denominator of which shall be equal to the Current
            Market Price on the Record Date, less an amount equal to the
            quotient of (x) the aggregate amount of such cash distribution and
            (y) the number of shares of Common Stock outstanding on the Record
            Date.

            Such increase shall become effective immediately prior to the
opening of business on the day following the Record Date for such distribution.
In the event that such distribution is not so made, the Conversion Rate shall
again be adjusted to be the Conversion Rate which would then be in effect if
such distribution had not been declared.

            (f)   In case a tender offer or exchange offer (other than as part
of a stock option exchange offer) made by the Company or any of its Subsidiaries
for all or any portion of the Common Stock shall expire, then and in each such
case, immediately prior to the opening of

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<PAGE>

business on the day after the date of the last time (the "EXPIRATION TIME")
tenders or exchanges could have been made pursuant to such tender offer or
exchange offer, the Conversion Rate shall be increased so that the same shall
equal the rate determined by multiplying the Conversion Rate in effect
immediately prior to the close of business on the date of the Expiration Time by
a fraction:

                  (A)   the numerator of which shall be the sum of (x) the
            product of (i) the number of shares of Common Stock outstanding
            (excluding any tendered or exchanged shares) at the Expiration Time
            and (ii) the Current Market Price of the Common Stock at the
            Expiration Time, and (y) the Fair Market Value of the aggregate
            consideration payable to stockholders based on acceptance (up to any
            maximum specified in the terms of the tender offer or exchange
            offer) of all shares validly tendered and not withdrawn as of the
            Expiration Time; and

                  (B)   the denominator of which shall be the product of the
            number of shares of Common Stock outstanding (including any tendered
            or exchanged shares) at the Expiration Time and the Current Market
            Price of the Common Stock at the Expiration Time.

            Such increase (if any) shall become effective immediately prior to
the opening of business on the day following the Expiration Time. In the event
that the Company is obligated to purchase shares pursuant to any such tender
offer or exchange offer, but the Company is permanently prevented by applicable
law from effecting any such purchases or all or a portion of such purchases are
rescinded, the Conversion Rate shall again be adjusted to be the Conversion Rate
which would then be in effect if such (or such portion of the) tender offer or
exchange offer had not been made. If the application of this Section 12.3(f) to
any tender offer or exchange offer would result in a decrease in the Conversion
Rate, no adjustment shall be made for such tender offer or exchange offer under
this Section 12.3(e).

            If the rights provided for in the Company's Rights Agreement dated
as of April 1, 1999 (the "STOCKHOLDER RIGHTS PLAN"), have separated from the
Common Stock in accordance with the provisions of the Stockholder Rights Plan so
that the Holders of the Notes would not be entitled to receive any rights in
respect of Common Stock issuable upon conversion of the Notes, the Conversion
Rate will be adjusted as provided in paragraph (d)(D) above, subject to
readjustment in the event of the expiration, termination or redemption of the
rights. In lieu of any such adjustment, the Company may amend the Stockholder
Rights Plan to provide that upon conversion of the Notes the Holders will
receive, in addition to the cash and Common Stock issuable upon such conversion,
the rights which would have attached to the shares of Common Stock issuable upon
conversion of the Notes solely into Common Stock at the then applicable
Conversion Rate if the rights had not become separated from the Common Stock
under the Stockholder Rights Plan. To the extent that the Company adopts any
future rights plan, upon conversion of the Notes, Holders will receive, in
addition to the cash and Common Stock issuable upon such conversion, the rights
under the future rights plan in respect of the shares of Common Stock issuable
upon conversion of the Notes solely into Common Stock at the then applicable
Conversion Price, whether or not the rights have separated from the Common Stock
at the time of conversion, and no adjustment to the Conversion Rate will be made
in connection with any distribution of rights thereunder.

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<PAGE>

            (g) For purposes of this ARTICLE XII, the following terms shall have
the meanings indicated:

            "CURRENT MARKET PRICE" on any date means the average of the daily
Closing Sale Prices per share of Common Stock for the ten consecutive Trading
Days immediately prior to such date; provided, however, that if:

            (i)   the "ex" date (as hereinafter defined) for any event (other
      than the issuance or distribution requiring such computation) that
      requires an adjustment to the Conversion Rate pursuant to Section 12.3(a),
      Section 12.3(b), Section 12.3(c), Section 12.3(d), Section 12.3(e) or
      Section 12.3(f) occurs during such ten consecutive Trading Days, the
      Closing Sale Price for each Trading Day prior to the "ex" date for such
      other event shall be adjusted by multiplying such Closing Sale Price by
      the same fraction by which the Conversion Rate is so required to be
      adjusted as a result of such other event;

            (ii)  the "ex" date for any event (other than the issuance or
      distribution requiring such computation) that requires an adjustment to
      the Conversion Rate pursuant to Section 12.3(a), Section 12.3(b), Section
      12.3(c), Section 12.3(d), Section 12.3(e) or Section 12.3(f) occurs on or
      after the "ex" date for the issuance or distribution requiring such
      computation and prior to the day in question, the Closing Sale Price for
      each Trading Day on and after the "ex" date for such other event shall be
      adjusted by multiplying such Closing Sale Price by the reciprocal of the
      fraction by which the Conversion Rate is so required to be adjusted as a
      result of such other event; and

            (iii) the "ex" date for the issuance or distribution requiring such
      computation is prior to the day in question, after taking into account any
      adjustment required pursuant to clause (1) or (2) of this proviso, the
      Closing Sale Price for each Trading Day on or after such "ex" date shall
      be adjusted by adding thereto the amount of any cash and the Fair Market
      Value (as determined by the Board of Directors in a manner consistent with
      any determination of such value for purposes of Section 12.3(d), Section
      12.3(e) or Section 12.3(f)) of the evidences of Indebtedness, shares of
      capital stock or assets being distributed applicable to one share of
      Common Stock as of the close of business on the day before such "ex" date.

For purposes of any computation under Section 12.3(f), if the "ex" date for any
event (other than the tender offer requiring such computation) that requires an
adjustment to the Conversion Rate pursuant to Section 12.3(a), Section 12.3(b),
Section 12.3(c), Section 12.3(d), Section 12.3(e) or Section 12.3(f) occurs on
or after the Expiration Time for the tender or exchange offer requiring such
computation and prior to the day in question, the Closing Sale Price for each
Trading Day on and after the "ex" date for such other event shall be adjusted by
multiplying such Closing Sale Price by the reciprocal of the fraction by which
the Conversion Rate is so required to be adjusted as a result of such other
event. For purposes of this paragraph, the term "ex" date, when used:

            (i)   with respect to any issuance or distribution, means the first
      date on which the Common Stock trade regular way on the relevant exchange
      or in the relevant market from which the Closing Sale Price was obtained
      without the right to receive such issuance or distribution;

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<PAGE>

            (ii)  with respect to any subdivision or combination of Common
      Stock, means the first date on which the Common Stock trade regular way on
      such exchange or in such market after the time at which such subdivision
      or combination becomes effective; and

            (iii) with respect to any tender offer or exchange offer, means the
      first date on which the Common Stock trade regular way on such exchange or
      in such market after the Expiration Time of such offer.

Notwithstanding the foregoing, whenever successive adjustments to the Conversion
Rate are called for pursuant to this Section 12.3, such adjustments shall be
made to the Current Market Price as may be necessary or appropriate to
effectuate the intent of this Section 12.3 and to avoid unjust or inequitable
results as determined in good faith by the Board of Directors.

            "FAIR MARKET VALUE" means the amount which a willing buyer would pay
a willing seller in an arm's length transaction (as determined by the Board of
Directors, whose determination shall be made in good faith and, absent manifest
error, shall be final and binding on Holders of the Securities).

            "RECORD DATE" means, with respect to any dividend, distribution or
other transaction or event in which the holders of Common Stock have the right
to receive any cash, securities or other property or in which the Common Stock
(or other applicable security) is exchanged for or converted into any
combination of cash, securities or other property, the date fixed for
determination of stockholders entitled to receive such cash, securities or other
property (whether such date is fixed by the Board of Directors or by statute,
contract or otherwise).

            (h) The Company shall be entitled to make such additional increases
in the Conversion Rate, in addition to those required by Section 12.3(a),
Section 12.3(b), Section 12.3(c), Section 12.3(d), Section 12.3(e) or Section
12.3(f) if the Board of Directors determines that it is advisable in order that
any dividend or distribution of Common Stock, any subdivision, reclassification
or combination of Common Stock or any issuance of rights or warrants referred to
above shall not be taxable to the holders of Common Stock for United States
federal income tax purposes.

            (i) To the extent permitted by applicable law, the Company may, from
time to time, increase the Conversion Rate by any amount for any period of time
if such period is at least 20 calendar days, the increase is irrevocable during
the period and the Board of Directors determine that such increase would be in
the best interests of the Company. Any such determination shall be conclusive,
absent manifest error. Whenever the Conversion Rate is increased pursuant to the
preceding sentence or clause (h) above, the Company shall mail to the Trustee
and each Holder at the address of such Holder as it appears in the Register, at
least 15 calendar days prior to the date the increased Conversion Rate takes
effect, a notice of the increase stating the increased Conversion Rate and the
period during which it shall be in effect.

            (j) In any case in which this Section 12.3 shall require that any
adjustment be made effective as of or retroactively immediately following a
Record Date, the Company may elect to defer (but only for five Trading Days
following the filing of the notice referred to in Section 12.5) issuing to the
Holder of any Securities converted after such Record Date the

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<PAGE>

Common Stock issuable upon such conversion over and above the Common Stock
issuable upon such conversion on the basis of the Conversion Rate prior to
adjustment; provided, however, that the Company shall deliver to such Holder a
due bill or other appropriate instrument evidencing such Holder's right to
receive such additional Common Stock upon the occurrence of the event requiring
such adjustment.

            (k) All calculations under this Section 12.3 shall be made to the
nearest cent or one-hundredth of a share, with one-half cent and 0.005 of a
share, respectively, being rounded upward. Notwithstanding any other provision
of this Section 12.3, the Company shall not be required to make any adjustment
of the Conversion Rate unless such adjustment would require an increase or
decrease of at least 1% in the Conversion Rate as last adjusted. Any lesser
adjustment shall be carried forward and shall be made at the time of and
together with the next subsequent adjustment which, together with any adjustment
or adjustments so carried forward, shall amount to an increase or decrease of at
least 1% in the Conversion Rate as last adjusted. Any adjustments under this
Section 12.3 shall be made successively whenever an event requiring such an
adjustment occurs.

            (l) In the event that at any time, as a result of an adjustment made
pursuant to this Section 12.3, the Holder of any Securities thereafter
surrendered for conversion shall become entitled to receive any shares of
Applicable Stock of the Company other than Common Stock into which the
Securities originally were convertible, the Conversion Rate of such other shares
so receivable upon conversion of any such Note shall be subject to adjustment
from time to time in a manner and on terms as nearly equivalent as practicable
to the provisions with respect to Common Stock contained in subparagraphs (a)
through (k) of this Section 12.3, and the provisions of Section 12.1, Section
12.2 and Section 12.4 through Section 12.9 with respect to the Common Stock
shall apply on like or similar terms to any such other shares (including,
without limitation, the determination of whether the conditions to conversion
provided in Section 12.1 have been satisfied). In the event that the Conversion
Rate is required to be adjusted pursuant to this Section 12.3 during any period
referred to in Section 12.1(a)(i) or any Cash Settlement Averaging Period, the
Closing Sale Price for each Trading Day during such period shall, to the extent
necessary, be adjusted to reflect the effects of such adjustment to this Section
12.3.

            (m) No adjustment shall be made pursuant to this Section 12.3 if the
effect thereof would be to reduce the Conversion Price below the par value (if
any) of the Common Stock.

      Section 12.4. Consolidation or Merger of the Company.

            If any of the following events occurs, namely:

            (a) any reclassification or change of the outstanding shares of
Common Stock (other than a change in par value, or from par value to no par
value, or from no par value to par value, or as a result of a subdivision or
combination);

            (b) any merger, consolidation, statutory share exchange or
combination of the Company with another Person as a result of which holders of
Common Stock shall be entitled to

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<PAGE>

receive securities, cash or other property with respect to or in exchange for
such Common Stock; or

            (c) any sale or conveyance of all or substantially all of the
properties and assets of the Company to any other Person as a result of which
holders of Common Stock shall be entitled to receive securities, cash or other
property with respect to or in exchange for such Common Stock;

the Company or the successor or purchasing Person, as the case may be, shall
execute with the Trustee a supplemental indenture (which shall comply with the
Trust Indenture Act as in force at the date of execution of such supplemental
indenture, if such supplemental indenture is then required to so comply)
providing that the Notes shall be convertible into the kind and amount of
securities, cash or other property which a Holder would have been entitled to
receive upon such reclassification, change, merger, consolidation, statutory
share exchange, combination, sale or conveyance had such Notes been converted
into Common Stock immediately prior to such reclassification, change, merger,
consolidation, statutory share exchange, combination, sale or conveyance
assuming such holder of Common Stock did not exercise its rights of election, if
any, as to the kind or amount of securities, cash or other property receivable
upon such merger, consolidation, statutory share exchange, combination, sale or
conveyance (provided, that if the kind or amount of securities, cash or other
property receivable upon such merger, consolidation, statutory share exchange,
combination, sale or conveyance is not the same for each share of Common Stock
in respect of which such rights of election shall not have been exercised
("NON-ELECTING SHARE"), then for the purposes of this Section 12.4, the kind and
amount of securities, cash or other property receivable upon such merger,
consolidation, statutory share exchange, combination, sale or conveyance for
each Non-Electing Share shall be deemed to be the kind and amount so receivable
per share by a plurality of the Non-Electing Shares). Such supplemental
indenture shall provide for adjustments which shall be as nearly equivalent as
may be practicable to the adjustments provided for in this ARTICLE XII and, to
the extent applicable, reflect the other types of adjustments provided for in
Section 12.3(l). If, in the case of any such reclassification, change, merger,
consolidation, statutory share exchange, combination, sale or conveyance, the
securities or property receivable thereupon by a holder of Common Stock includes
shares of stock or other securities or property of a Person other than the
successor or purchasing Person, as the case may be, in such reclassification,
change, merger, consolidation, statutory share exchange, combination, sale or
conveyance, then such supplemental indenture shall also be executed by such
other Person and shall contain such additional provisions to protect the
interests of the Holders of the Notes as the Board of Directors shall reasonably
consider necessary by reason of the foregoing including the provisions providing
for the purchase rights set forth in ARTICLE IV and ARTICLE V.

            The Company shall cause notice of the execution of such supplemental
indenture to be mailed to each Holder, at the address of such Holder as it
appears on the Register, within 20 days after execution thereof. Failure to
deliver such notice shall not affect the legality or validity of such
supplemental indenture.

            The above provisions of this Section 12.4 shall similarly apply to
successive reclassifications, changes, mergers, consolidations, statutory share
exchanges, combinations, sales and conveyances.

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<PAGE>

            If this Section 12.4 applies to any event or occurrence, Section
12.3 shall not apply.

      Section 12.5. Notice of Adjustment.

            Whenever an adjustment in the Conversion Rate with respect to the
Securities is required:

            (a) the Company shall forthwith place on file with the Trustee and
any Conversion Agent for such securities a certificate of the Chief Financial
Officer of the Company, stating the adjusted Conversion Rate determined as
provided herein and setting forth in reasonable detail such facts as shall be
necessary to show the reason for and the manner of computing such adjustment;
and

            (b) a notice stating that the Conversion Rate has been adjusted and
setting forth the adjusted Conversion Rate shall forthwith be given by the
Company or, at the Company's request, by the Trustee in the name and at the
expense of the Company, to each Holder in the manner provided in Section 13.2.
Any notice so given shall be conclusively presumed to have been duly given,
whether or not the Holder receives such notice.

      Section 12.6. Notice in Certain Events.

            In case of:

            (a) a consolidation or merger to which the Company is a party and
for which approval of any stockholders of the Company is required, or of the
sale or conveyance to another Person or group of Persons acting in concert as a
partnership, limited partnership, syndicate or other group (within the meaning
of Rule 13d-3 under the Exchange Act) of all or substantially all of the
property and assets of the Company; or

            (b) the voluntary or involuntary dissolution, liquidation or winding
up of the Company; or

            (c) any action triggering an adjustment of the Conversion Rate
referred to in clauses (x) or (y) below; then, in each case, the Company shall
cause to be filed with the Trustee and the Conversion Agent, and shall cause to
be given, to the Holders of the Securities in the manner provided in Section
13.2, at least 15 days prior to the applicable date hereinafter specified, a
notice stating:

            (x) the date on which a record is to be taken for the purpose of any
      distribution or grant of rights or warrants triggering an adjustment to
      the Conversion Rate pursuant to this ARTICLE XII, or, if a record is not
      to be taken, the date as of which the holders of record of Common Stock
      entitled to such distribution, rights or warrants are to be determined; or

            (y) the date on which any reclassification, consolidation, merger,
      sale, conveyance, dissolution, liquidation or winding up triggering an
      adjustment to the

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<PAGE>

      Conversion Rate pursuant to this ARTICLE XII is expected to become
      effective, and the date as of which it is expected that holders of Common
      Stock of record shall be entitled to exchange their shares of Common Stock
      for securities or other property deliverable upon such reclassification,
      consolidation, merger, sale, conveyance, dissolution, liquidation or
      winding up.

            Failure to give such notice or any defect therein shall not affect
the legality or validity of the proceedings described in Section 12.6(a),
Section 12.6(b) or Section 12.6(c).

      Section 12.7. Company to Reserve Stock: Registration; Listing.

            (a) The Company shall, prior to issuance of any Securities
hereunder, and from time to time as may be necessary, reserve and keep
available, free from preemptive rights, out of its authorized but unissued
Common Stock, for the purpose of effecting the conversion of the Securities,
such number of its duly authorized Common Stock as shall from time to time be
sufficient to effect the conversion of all Securities then outstanding into such
Common Stock at any time (assuming that, at the time of the computation of such
number of Common Stock, all such Securities would be held by a single Holder).
The Company covenants that all Common Stock which may be issued upon conversion
of Securities shall upon issue be fully paid and nonassessable and free from all
liens and charges and, except as provided in Section 12.8, taxes with respect to
the issue thereof.

            (b) If any shares of Applicable Stock which would be issuable upon
conversion of Securities hereunder (including, without limitation, in connection
with any transaction referred to in Section 12.4) require registration with or
approval of any governmental authority before such shares may be issued upon
such conversion, the Company shall use its reasonable best efforts to cause such
shares to be duly registered or approved, as the case may be. In addition, in
connection with any transaction referred to in Section 12.4, the Company and any
parent company of the Company required to issue Applicable Stock upon conversion
of a Note shall take such actions as are required to entitle the Company or such
parent company, as the case may be, to rely on Section 3(a)(9) of the Securities
Act in connection with conversion of the Securities without extending any
holding periods under Rule 144 or otherwise permit such Applicable Stock issued
upon conversion of the Securities to be resold without requiring registration
thereof under the Securities Act.

            (c) The Company further covenants that so long as the Common Stock
shall be listed on the New York Stock Exchange, the Company shall use its
reasonable best efforts, if permitted by the rules of the New York Stock
Exchange, to keep so listed all Common Stock issuable upon conversion of the
Securities, and the Company shall use its reasonable best efforts to list or
obtain approval for the quotation of the Common Stock to be delivered upon
conversion of the Securities prior to such delivery upon any other national
securities exchange or quotation system upon which the outstanding Common Stock
is listed or quoted at the time of such delivery.

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<PAGE>

      Section 12.8. Taxes on Conversion.

            The issue of stock certificates on conversion of Securities shall be
made without charge to the converting Holder for any documentary, stamp or
similar issue or transfer taxes in respect of the issue thereof, and the Company
shall pay any and all documentary, stamp or similar issue or transfer taxes that
may be payable in respect of the issue or delivery of Common Stock on conversion
of Securities pursuant hereto. The Company shall not, however, be required to
pay any tax which may be payable in respect of any transfer involved in the
issue or delivery of Common Stock or the portion, if any, of the Securities
which are not so converted in a name other than that in which the Securities so
converted were registered, and no such issue or delivery shall be made unless
and until the Person requesting such issue has paid to the Company the amount of
such tax or has established to the satisfaction of the Company that such tax has
been paid.

      Section 12.9. Conversion After Regular Record Date.

            Except as provided in the succeeding paragraph, upon conversion, the
Holder of Securities shall not be entitled to receive any accrued and unpaid
interest, Additional Amounts or Additional Interest, if any.

            If any Securities are surrendered for conversion subsequent to the
close of business on any Regular Record Date but prior to the opening of
business on the corresponding Interest Payment Date, the Holder of such
Securities at the close of business on such Regular Record Date shall receive
the interest, Additional Amounts and Additional Interest, if any, payable on
such Securities on such Interest Payment Date notwithstanding the conversion
thereof. Securities surrendered for conversion during the period from the close
of business on any Regular Record Date to the opening of business on the
corresponding Interest Payment Date shall (except in the case of Securities
which have been called for redemption on a Redemption Date within such period or
Securities surrendered for conversion after acceleration of the Securities) be
accompanied by payment by Holders, for the account of the Company, in New York
Clearing House funds or other funds acceptable to the Company of an amount equal
to the interest, Additional Amounts and Additional Interest, if any, payable on
such interest payment date on the Securities being surrendered for conversion.

            Except as described in Section 12.2(a) and this Section 12.9, the
Company will not make any payment in cash or Common Stock or other adjustment
for accrued and unpaid interest, Additional Amounts or Additional interest on
any Securities when they are converted.

      Section 12.10. Company Determination Final.

            The Company or its agents shall be responsible for making all
calculations required under the terms of this ARTICLE XII. Any determination
that the Company or the Board of Directors must make pursuant to this ARTICLE
XII shall be made in good faith and, absent manifest error, shall be final and
binding on holders of the Securities. The Company or its agents shall be
required to deliver to the Trustee a schedule of its calculations and the
Trustee shall be entitled to conclusively rely upon the accuracy of such
calculations without independent verification.

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<PAGE>

      Section 12.11. Responsibility of Trustee for Conversion Provisions.

            The Trustee has no duty to determine when an adjustment under this
ARTICLE XII should be made, how it should be made or what it should be. The
Trustee makes no representation as to the validity or value of any securities or
assets issued upon conversion of Securities. The Trustee shall not be
responsible for any failure of the Company to comply with this ARTICLE XII. Each
Conversion Agent other than the Company shall have the same protection under
this Section 12.11 as the Trustee.

            The rights, privileges, protections, immunities and benefits given
to the Trustee under this Indenture including, without limitation, its rights to
be indemnified, are extended to, and shall be enforceable by, other than the
Company, the Trustee in each of its capacities hereunder, and each Paying Agent,
Registrar or Conversion Agent, other than the Company, acting hereunder.

      Section 12.12. Unconditional Right of Holders to Convert.

            Notwithstanding any other provision in this Indenture, the Holder of
any Note shall have the right, which is absolute and unconditional, to convert
its Note in accordance with this ARTICLE XII and to bring an action against the
Company for the enforcement of any such right to convert, and such rights shall
not be impaired or affected without the consent of such Holder.

      Section 12.13. Option to Satisfy Conversion Obligation with Cash, Common
Stock or Combination Thereof.

            (a) If the Company receives any Holder's Conversion Notice on or
prior to the day that is 31 Trading Days prior to the Stated Maturity (the
"FINAL NOTICE DATE"), then (i) as to the principal amount of the Security, the
method for settlement shall be in accordance with the Principal Conversion
Settlement Election and (ii) as to the Excess Amount, the Company shall notify
the Holder through the Trustee, at any time on or before the date that is three
Trading Days following receipt of the Conversion Notice required pursuant to
Section 12.2 (such period, the "SETTLEMENT NOTICE PERIOD") of the method the
Company elects to settle its obligation upon conversion of the Excess Amount
(the "EXCESS AMOUNT CONVERSION OBLIGATION", which together with the obligation
upon conversion in respect of principal, constitutes the "CONVERSION
OBLIGATION"). Specifically, the Company shall notify the Holders through the
Trustee whether a Holder submitting a Conversion Notice is entitled to receive,
in respect of the Excess Amount Conversion Obligation, 100% cash, 100 % Common
Stock, or a combination of cash and Common Stock. If the Company elects to
settle the Excess Amount Conversion Obligation in a combination of cash and
Common Stock, the Company will specify the percentage of each obligation to be
settled in cash. The Company shall treat all Holders converting on the same
Trading Day in the same manner, and the Company shall not have any obligation to
settle Excess Amount Conversion Obligations arising on different Trading Days in
the same manner.

            Settlement of the Company's entire Conversion Obligation in Common
Stock only shall occur in accordance with Section 12.2(a). Settlement in cash or
in a combination of cash and Common Stock shall, subject to Section 12.13(c),
occur on the third Trading Day

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<PAGE>

following the final Trading Day of the 20 Trading Day period beginning on the
final Trading Day of the Settlement Notice Period (the "CASH SETTLEMENT
AVERAGING PERIOD").

            Settlement amounts shall be computed as follows:

            (i)   if the Company elects to satisfy its entire Conversion
      Obligation, including principal amount and Excess Amount, in shares of
      Common Stock (other than with respect to fractional shares), the Company
      shall deliver to a Holder a number of shares of Common Stock equal to the
      product of (1) the aggregate principal amount of the Securities to be
      converted divided by 1,000, multiplied by (2) the applicable Conversion
      Rate;

            (ii)  if the Company elects to satisfy its entire Conversion
      Obligation in cash, including principal amounts at Issuance and Excess
      Amount, the Company shall deliver to a Holder cash in an amount equal to
      the product of (1) the product of (x) the aggregate principal amount of
      Securities to be converted divided by 1,000, multiplied by (y) the
      applicable Conversion Rate multiplied by (2) the arithmetic average of the
      Closing Sale Prices of the Common Stock during the Cash Settlement
      Averaging Period;

            (iii) if the Company elects to satisfy its Conversion Obligation,
      including principal amount and Excess Amount, in a combination of cash and
      Common Stock, the Company shall deliver to a Holder:

                        (1)   a cash amount (the "CASH AMOUNT") (excluding any
                  cash in lieu of fractional shares) equal to the product of:

                              (A) the percentage of the Conversion Obligation to
                  be satisfied in cash, multiplied by

                              (B) the amount of cash that would be paid pursuant
                  to clause (ii) immediately above;

                        (2)   a number of shares of Common Stock equal to the
                  remainder of:

                              (A) the number of shares of Common Stock that
                  would be issued pursuant to clause (i) immediately above,
                  minus

                              (B) the number of shares of Common Stock equal to
                  the quotient of (x) the Cash Amount divided by (y) the
                  arithmetic average of the Closing Sale Prices of the Common
                  Stock during the Cash Settlement Averaging Period.

            (b) The Company shall settle all of its Conversion Obligations
arising after the Final Notice Date in the same manner. Settlement of the
Conversion Obligation relating to the principal amount of the Securities shall
be according to the Principal Conversion Settlement Election. On or prior to the
Final Notice Date, the Company shall notify the Holders through the

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<PAGE>

Trustee of the method it chooses to settle any Excess Amount Conversion
Obligations arising after the Final Notice Date.

            Settlement of Conversion Obligations arising after the Final Notice
Date in Common Stock only shall be made in accordance with Section 12.2(a).
Subject to Section 12.13(c), settlement of Conversion Obligations arising after
the Final Notice Date in cash or in a combination of cash and Common Stock shall
be made on the third Trading Day following the final Trading Day of the Cash
Settlement Averaging Period described in the following sentence. The settlement
amount of Common Stock, cash or combination of cash and Common Stock in
satisfaction of Conversion Obligations arising after the Final Notice Date shall
be computed in the same manner as set forth in Section 12.13(a), except that the
"Cash Settlement Averaging Period" shall be the 20 Trading Day period beginning
on the date that is the 23rd Trading Day prior to the Stated Maturity.

            (c) If any Trading Day during a Cash Settlement Averaging Period is
not an Undisrupted Trading Day, then determination of the price for that day
will be delayed until the next Undisrupted Trading Day on which a pricing is not
otherwise observed and such day will not count as one of the 20 Trading Days
that constitute the Cash Settlement Averaging Period. If this results in a price
being observed later than the eighth Trading Day after the last of the original
20 Trading Days in the Cash Settlement Averaging Period, then the Company shall
determine all prices for all delayed and undetermined prices on that eighth
Trading Day based on its good faith estimate of the value of the Common Stock on
that date. In the event that any Trading Day during the Cash Settlement
Averaging Period beginning on the date that is the 23rd Trading Day prior to the
Stated Maturity is not an Undisrupted Trading Day, settlement will occur after
the Stated Maturity.

                                  ARTICLE XIII

                                 MISCELLANEOUS

      Section 13.1. Trust Indenture Act Controls. If any provision of this
Indenture limits, qualifies, or conflicts with the duties imposed by Section
318(c) of the TIA, such section of the TIA shall control. If any provision of
this Indenture expressly modifies or excludes any provision of the TIA that may
be so modified or excluded under the TIA, the Indenture provision so modifying
or excluding such provision of the TIA shall be deemed to apply.

      Section 13.2. Notices. Any request, demand, authorization, notice, waiver,
consent or communication shall be in writing, in the English language and
delivered in person (including by commercial courier services) or mailed by
first-class mail, postage prepaid, addressed as follows or transmitted by
facsimile transmission (confirmed by guaranteed overnight courier) to the
following facsimile numbers:

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<PAGE>

      if to the Company:

      WILLBROS GROUP, INC.
      c/o Willbros USA, Inc.
      4400 Post Oak Parkway, Suite 1000
      Houston, Texas 77027
      Attention:  Chief Financial Officer
      Facsimile No.: (713) 403-8010

      if to the Trustee:

      JPMORGAN CHASE BANK
      600 Travis Street, Suite 1150
      Houston, Texas 77002
      Attention: Institutional Trust Services
      Facsimile No.: (713) 577-5200

            The Company or the Trustee by notice given to the other in the
manner provided above may designate additional or different addresses for
subsequent notices or communications.

            Any notice or communication given to a Holder shall be mailed to the
Holder, by first-class mail, postage prepaid, at the Holder's address as it
appears on the Register and shall be sufficiently given if so mailed within the
time prescribed.

            Failure to mail a notice or communication to a Holder or any defect
in it shall not affect its sufficiency with respect to other Holders. If a
notice or communication is mailed in the manner provided above and within the
time prescribed, it is duly given, whether or not received by the addressee.

            If the Company mails a notice or communication to the Holders, it
shall mail a copy to the Trustee and each Registrar, Paying Agent, Conversion
Agent or co-registrar.

      Section 13.3. Communication by Holders with Other Holders.

            Holders may communicate pursuant to Section 312(b) of the TIA with
other Holders with respect to their rights under this Indenture or the
Securities. The Company, the Trustee, the Registrar, the Paying Agent, the
Conversion Agent and anyone else shall have the protection of TIA Section
312(c).

      Section 13.4. Certificate and Opinion as to Conditions Precedent.

            Upon any request or application by the Company to the Trustee to
take any action under this Indenture (except in connection with the original
issuance of Securities), the Company shall furnish to the Trustee:

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<PAGE>

            (a) an Officers' Certificate stating that, in the opinion of the
signers, all conditions precedent, if any, provided for in this Indenture
relating to the proposed action have been complied with; and

            (b) an Opinion of Counsel stating that, in the opinion of such
counsel, all such conditions precedent have been complied with.

      Section 13.5. Statements Required in Certificate or Opinion.

            Each Officers' Certificate or Opinion of Counsel with respect to
compliance with a covenant or condition provided for in this Indenture shall
include:

            (a) a statement that each person making such Officers' Certificate
or Opinion of Counsel has read such covenant or condition;

            (b) a brief statement as to the nature and scope of the examination
or investigation upon which the statements or opinions contained in such
Officers' Certificate or Opinion of Counsel are based;

            (c) a statement that, in the opinion of each such person, he has
made such examination or investigation as is necessary to enable such person to
express an informed opinion as to whether or not such covenant or condition has
been complied with; and

            (d) a statement that, in the opinion of such person, such covenant
or condition has been complied with.

            In giving such Opinion of Counsel, counsel may rely as to factual
matters on an Officers' Certificate or on certificates of public officials.

      Section 13.6. Separability Clause.

            In case any provision in this Indenture or in the Securities shall
be invalid, illegal or unenforceable, the validity, legality and enforceability
of the remaining provisions shall not in any way be affected or impaired
thereby.

      Section 13.7. Rules by Trustee, Paying Agent, Conversion Agent, Registrar.

            The Trustee may make reasonable rules for action by or a meeting of
Holders. The Registrar, the Conversion Agent and the Paying Agent may make
reasonable rules for their functions.

      Section 13.8. Legal Holidays.

            If any specified date (including a date for giving notice) is a
Legal Holiday, the action shall be taken on the next succeeding day that is not
a Legal Holiday, and, if the action to be taken on such date is a payment in
respect of the Securities, no interest, if any, shall accrue for the intervening
period.

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<PAGE>

      Section 13.9. Governing Law; Submission to Jurisdiction; Service of
Process.

            This Indenture shall be governed by, and construed in accordance
with, the laws of the State of New York.

            The Company submits to the non-exclusive jurisdiction of the
competent courts of the State of New York and the courts of the United States of
America, in each case located in the Borough of Manhattan, New York, New York
over any suit, action or proceeding arising under or in connection with this
Indenture or the transactions contemplated hereby or the Securities. The Company
waives any objection that it may have to the venue of any suit, action or
proceeding arising under or in connection with this Indenture or the
transactions contemplated hereby or the Securities in the courts of the State of
New York or the courts of the United States of America, in each case located in
the Borough of Manhattan, New York, New York, or that such suit, action or
proceeding brought in the courts of the State of New York or the courts of the
United States of America, in each case located in the Borough of Manhattan, New
York, New York, was brought in an inconvenient court and agrees not to plead or
claim the same. In furtherance of the foregoing, the Company hereby irrevocably
designates and appoints CT Corporation, 111 Eighth Avenue, New York, New York
10011, as the agent of the Company to receive service of all process brought
against the Company with respect to any such suit, action or proceeding in any
such court in the Borough of Manhattan, New York, New York, such service being
hereby acknowledged by the Company to be effective and binding service in every
respect. Copies of any such process so served shall also be given to the Company
in accordance with Section 13.2 hereof, but the failure of the Company to
receive such copies shall not affect in any way the service of such process as
aforesaid. On the Issue Date, the Company shall furnish to the Trustee a consent
of CT Corporation agreeing to act hereunder. If for any reason CT Corporation
shall resign or otherwise cease to act as such agent, the Company hereby
irrevocably agrees to (i) immediately designate and appoint a new agent
reasonably acceptable to the Trustee to serve in such capacity and, in such
event, such new agent shall be deemed to be substituted for CT Corporation for
all purposes hereof and (ii) promptly deliver to the Trustee the written consent
(in form and substance reasonably satisfactory to the Trustee) of such new agent
agreeing to serve in such capacity.

            Nothing in this Section 13.9 shall limit the right of the Trustee or
any Holder to bring proceedings against the Company in the courts of any other
jurisdiction or to serve process in any other manner permitted by law.

      Section 13.10. No Recourse Against Others.

            No recourse under or upon any obligation, covenant or agreement
contained in this Indenture, or in any Security, or because of any indebtedness
evidenced thereby, shall be had against any incorporator, as such, or against
any past, present or future stockholder, officer or director, as such, of the
Company or of any successor, either directly or through the Company or any
successor, under any rule of law, statute or constitutional provision or by the
enforcement of any assessment or by any legal or equitable proceeding or
otherwise, all such liability being expressly waived and released by the
acceptance of the Securities by the Holders and as part of the consideration for
the issue of the Securities.

                                       85
<PAGE>

      Section 13.11. Successors.

            All agreements of the Company in this Indenture and the Securities
shall bind its successor. All agreements of the Trustee in this Indenture shall
bind its successor.

      Section 13.12. Multiple Originals.

            The parties may sign any number of copies of this Indenture. Each
signed copy shall be an original, but all of them together represent the same
agreement. One signed copy is enough to prove this Indenture.

      Section 13.13. Table of Contents, Headings, Etc.

            The Table of Contents and the headings of the Articles or Sections
of this Indenture have been inserted for convenience of reference only, are not
to be considered a part of this Indenture and shall in no way modify or restrict
any of the terms or provisions hereof.

                                    * * * *

                                       86
<PAGE>

            IN WITNESS WHEREOF, the undersigned, being duly authorized, have
executed this Indenture on behalf of the respective parties hereto as of the
date first above written.

                                    WILLBROS GROUP, INC.

                                    By: /s/ Michael F. Curran
                                        ----------------------------
                                    Name:  Michael F. Curran
                                    Title: President and Chief Executive Officer

                                    JPMORGAN CHASE BANK, as Trustee

                                    By: /s/ Frank W. McCreary
                                        ----------------------------
                                    Name:  Frank W. McCreary
                                    Title: Authorized Signatory

                          SIGNATURE PAGE TO INDENTURE

<PAGE>

                                   EXHIBIT A

                             [FORM OF FACE OF NOTE]

            [UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED
REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY TO THE ISSUER OR ITS AGENT FOR
REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS
REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN
AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY (AND ANY PAYMENT
HEREON IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN
AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY), ANY TRANSFER, PLEDGE
OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL SINCE
THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN. THIS SECURITY
IS A GLOBAL SECURITY WITHIN THE MEANING OF THE INDENTURE HEREINAFTER REFERRED TO
AND IS REGISTERED IN THE NAME OF A DEPOSITARY OR A NOMINEE THEREOF. THIS
SECURITY IS EXCHANGEABLE FOR SECURITIES REGISTERED IN THE NAME OF A PERSON OTHER
THAN THE DEPOSITARY OR ITS NOMINEE ONLY IN THE LIMITED CIRCUMSTANCES DESCRIBED
IN THE INDENTURE AND, UNLESS AND UNTIL IT IS EXCHANGED IN WHOLE OR IN PART FOR
SECURITIES IN CERTIFICATED FORM, THIS SECURITY MAY NOT BE TRANSFERRED EXCEPT AS
A WHOLE BY THE DEPOSITARY TO A NOMINEE OF THE DEPOSITARY OR BY A NOMINEE OF THE
DEPOSITARY TO THE DEPOSITARY OR ANOTHER NOMINEE OF THE DEPOSITARY OR BY THE
DEPOSITARY OR ANY SUCH NOMINEE TO A SUCCESSOR DEPOSITARY OR A NOMINEE OF SUCH
SUCCESSOR DEPOSITARY.](1)

      [THE SECURITY EVIDENCED BY THIS CERTIFICATE HAS NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT OF 1933"), OR ANY
STATE SECURITIES LAWS, AND MAY NOT BE OFFERED OR SOLD EXCEPT AS SET FORTH IN THE
FOLLOWING SENTENCE. BY ACQUISITION HEREOF, THE HOLDER:

            (1)   REPRESENTS THAT (A) IT IS A "QUALIFIED INSTITUTIONAL BUYER" AS
      DEFINED IN RULE 144A UNDER THE SECURITIES ACT OF 1933 OR (B) IT IS AN
      INSTITUTIONAL INVESTOR THAT IS AN "ACCREDITED INVESTOR" AS DEFINED IN RULE
      501(A)(1), (2), (3) OR (7) UNDER THE SECURITIES ACT OF 1933 (AN
      "INSTITUTIONAL ACCREDITED INVESTOR");

            (2)   AGREES THAT IT WILL NOT, WITHIN TWO YEARS AFTER THE LATEST
      DATE OF THE ORIGINAL ISSUANCE OF THE NOTES, RESELL OR OTHERWISE TRANSFER
      THE SECURITY EVIDENCED HEREBY OR THE SHARES OF COMMON STOCK ISSUABLE UPON
      CONVERSION OF SUCH SECURITY EXCEPT (A) TO THE COMPANY OR ANY SUBSIDIARY
      THEREOF,

--------------------
(1) This legend should be included only if the Note is a Global Security.

                                      A-1
<PAGE>

      (B) TO A PERSON THAT THE HOLDER REASONABLY BELIEVES IS A "QUALIFIED
      INSTITUTIONAL BUYER" AS DEFINED IN, AND IN COMPLIANCE WITH, RULE 144A
      UNDER THE SECURITIES ACT OF 1933, (C) PURSUANT TO THE EXEMPTION FROM
      REGISTRATION PROVIDED BY RULE 144 UNDER THE SECURITIES ACT OF 1933 (IF
      AVAILABLE), (D) PURSUANT TO AN EXEMPTION FROM THE REGISTRATION
      REQUIREMENTS OF THE SECURITIES ACT OF 1933 (IF AVAILABLE) TO AN
      INSTITUTIONAL ACCREDITED INVESTOR THAT, PRIOR TO SUCH TRANSFER, FURNISHES
      TO JPMORGAN CHASE BANK, AS TRUSTEE (OR ANY SUCCESSOR TRUSTEE, AS
      APPLICABLE), SUCH CERTIFICATIONS AND OPINION OF COUNSEL REQUIRED BY THE
      COMPANY OR THE TRUSTEE OR (E) PURSUANT TO A REGISTRATION STATEMENT THAT
      HAS BEEN DECLARED EFFECTIVE UNDER THE SECURITIES ACT OF 1933, AS AMENDED,
      AND THAT CONTINUES TO BE EFFECTIVE AT THE TIME OF SUCH TRANSFER; AND

            (3)   AGREES THAT IT WILL DELIVER TO EACH PERSON TO WHOM THE
      SECURITY EVIDENCED HEREBY IS TRANSFERRED (OTHER THAN A TRANSFER PURSUANT
      TO CLAUSE 2(A), 2(C) OR 2(E) ABOVE), A NOTICE SUBSTANTIALLY TO THE EFFECT
      OF THIS LEGEND.](2)

            [THE HOLDER OF THIS SECURITY IS ENTITLED TO THE BENEFITS OF A
REGISTRATION RIGHTS AGREEMENT (AS SUCH TERM IS DEFINED IN THE INDENTURE REFERRED
TO ON THE REVERSE HEREOF) AND, BY ITS ACCEPTANCE HEREOF, AGREES TO BE BOUND BY
AND TO COMPLY WITH THE PROVISIONS OF SUCH REGISTRATION RIGHTS AGREEMENT.](2)

------------------
(2) This legend should be included only if the Note is a Transfer Restricted
Security.

                                      A-2
<PAGE>

                              WILLBROS GROUP, INC.

                     2.75% CONVERTIBLE SENIOR NOTE DUE 2024

                                                              $_________________

No. ___                                                          CUSIP:_________

      WILLBROS GROUP, INC., a Panamanian corporation (the "Company", which term
shall include any successor Person under the Indenture referred to on the
reverse hereof), for value received, promises to pay to _____________________,
or registered assigns, on March 15, 2024, the principal amount of
________________ Dollars ($______________) [, or such greater or lesser
principal amount as is indicated in the records of the Trustee and the
Depositary](3).

      In addition, for value received, the Company hereby promises to pay to the
Holder of this Note, or registered assigns, from March 12, 2004, or from the
most recent Interest Payment Date to which interest has been paid or provided
for, to, but not including, March 15, 2024, interest at an annual rate of 2.75%
of the principal amount of this Note. Interest on this Note is payable in cash
semi-annually in arrears on March 15 and September 15 in each year (each, an
"INTEREST PAYMENT DATE"), with the first Interest Payment Date being September
15, 2004. Each payment of interest on this Note will include interest accrued
through the day before the applicable Interest Payment Date.

      The interest so payable, and punctually paid or duly provided for, on any
Interest Payment Date shall, except as provided in the Indenture, be paid to the
Person in whose name this Note (or one or more predecessor Notes) is registered
at the close of business on the regular record date for such interest, which
shall be the March 1 or September 1 (whether or not a Business Day), as the case
may be, next preceding the corresponding Interest Payment Date (a "REGULAR
RECORD DATE"). Any such interest, Additional Amounts and Additional Interest,
not so punctually paid or duly provided for shall forthwith cease to be payable
to the Holder on such Regular Record Date and may be paid (a) to the Person in
whose name this Note (or one or more predecessor Notes) is registered at the
close of business on a special record date for the payment of such defaulted
interest to be fixed by the Trustee (a "SPECIAL RECORD DATE"), notice whereof
shall be given to Holders not less than 10 days prior to such Special Record
Date, or (b) at any time in any other lawful manner not inconsistent with the
requirements of any securities exchange on which the Notes may be listed, and
upon such notice as may be required by such exchange, all as more fully provided
in the Indenture.

      Reference is hereby made to the further provisions of this Note set forth
on the reverse side of this Note, which further provisions shall for all
purposes have the same effect as if set forth at this place.

-------------------
(3) This phrase should be included only if the Note is a Global Security.

                                      A-3
<PAGE>

            IN WITNESS WHEREOF, the Company has caused this instrument to be
duly executed.

                                      WILLBROS GROUP, INC.

                                      By:  ________________________

                                      Name: _______________________

                                      Title: _________

                                      A-4
<PAGE>

                    TRUSTEE'S CERTIFICATE OF AUTHENTICATION

      This is one of the Notes referred to in the within-mentioned Indenture.

Dated:                                 JPMORGAN CHASE BANK,
                                       as Trustee

                                       By:________________________
                                          Authorized Signatory

                                      A-5
<PAGE>

                           [FORM OF REVERSE OF NOTE]

                    2.75 % CONVERTIBLE SENIOR NOTE DUE 2024

            This Note is one of a duly authorized issue of 2.75 % Convertible
Senior Notes due 2024 (the "Notes") of WILLBROS GROUP, INC., a Panamanian
corporation (including any successor corporation under the Indenture hereinafter
referred to, the "Company"), issued under an Indenture, dated as of March 12,
2004 (the "Indenture"), between the Company and JPMORGAN CHASE BANK, a New York
banking corporation, as Trustee (the "Trustee"). The terms of the Note include
those stated in the Indenture, those made part of the Indenture by reference to
the Trust Indenture Act of 1939, as amended ("TIA"), and those set forth in this
Note. This Note is subject to all such terms, and Holders are referred to the
Indenture and the TIA for a statement of all such terms. Capitalized terms used
but not defined herein have the meanings assigned to them in the Indenture
referred to below unless otherwise indicated.

1.    Interest.

            Interest on the Notes shall be computed on the basis of a 360-day
year of twelve 30-day months.

            If this Note is redeemed pursuant to Section 5 of this Note or the
Holder elects to require the Company to purchase this Note pursuant to Section 6
of this Note, on a date that is after the Regular Record Date and on or before
the corresponding Interest Payment Date, interest, Additional Amounts and
Additional Interest, if any, accrued and unpaid hereon to, but excluding, the
applicable Redemption Date, Purchase Date or Fundamental Change Purchase Date
shall be paid to the same Holder to whom the Company pays the principal of this
Note. Interest, Additional Amounts and Additional Interest, if any, accrued and
unpaid hereon at the Stated Maturity also shall be paid to the same Holder to
whom the Company pays the principal of this Note.

            Interest, Additional Amounts and Additional Interest, if any, on
Notes converted after the close of business on a Regular Record Date but prior
to the opening of business on the corresponding Interest Payment Date shall be
paid to the Holder of the Notes on the Regular Record Date but, upon conversion,
the Holder must pay the Company an amount equal to the interest, Additional
Amounts and Additional Interest, if any, which has accrued and shall be paid on
such Interest Payment Date. No such payment need be made with respect to Notes
converted after a Regular Record Date and prior to the corresponding Interest
Payment Date after being called for redemption or upon acceleration.

            All references herein to interest accrued or payable as of any date
shall, without duplication, be deemed to include Additional Amounts and
Additional Interest, if any, payable pursuant to the Registration Rights
Agreement.

2.    Method of Payment.

            All payments of cash due on the Notes shall be in such coin or
currency of the United States of America as at the time of payment is legal
tender for payment of public and private debts. The Holder must surrender the
Notes to the Paying Agent to collect payment of

                                      A-6
<PAGE>

principal. Payment of interest on Certificated Securities in the aggregate
principal amount of $5,000,000 or less shall be made by check mailed to the
address of the Person entitled thereto as such address appears in the Register,
and payment of interest on Certificated Securities in aggregate principal amount
in excess of $5,000,000 shall be made by wire transfer in immediately available
funds at the election of such Holder. Notwithstanding the foregoing, so long as
the Notes are registered in the name of a Depositary or its nominee, all cash
payments with respect to the Notes shall be made by wire transfer of immediately
available funds to the account of the Depositary or its nominee. At the Stated
Maturity, interest, Additional Amounts and Additional Interest, if any, on
Certificated Securities will be payable at the office or agency of the Company
described in the Indenture.

3.    Paying Agent, Registrar, Conversion Agent.

            Initially, JPMorgan Chase Bank shall act as Paying Agent, Registrar
and Conversion Agent. The Company may appoint and change any Paying Agent,
Registrar and Conversion Agent without notice, other than notice to the Trustee;
provided that the Company shall maintain at least one Paying Agent, Registrar
and Conversion Agent in the Borough of Manhattan, New York, New York, which
shall initially be the Corporate Trust Office of the Trustee.

4.    Indenture.

            The Notes are general senior obligations of the Company limited to
up to $70,000,000 aggregate principal amount. The Indenture does not limit other
indebtedness of the Company, secured or unsecured.

5.    Redemption of the Notes by the Company.

            Subject to the terms and conditions of the Indenture, the Company
may, at its option, redeem for cash (i) all or a portion of the Notes at any
time beginning on March 15, 2011, at a Redemption Price equal to 100% of the
principal amount of the Notes plus accrued and unpaid interest, Additional
Amounts and Additional Interest, if any, to, but not including, the Redemption
Date, and (ii) all of the Notes at any time at a Redemption Price equal to 100%
of the principal amount of the Notes plus accrued and unpaid interest,
Additional Amounts and Additional Interest, if any, to, but not including, the
Redemption Date, in the event of certain changes affecting tax laws described in
clause (ii) of Section 3.1 of the Indenture, subject to the option of each
Holder to avoid such redemption with respect to its Notes as provided in such
Section.

            At least 20 days but not more than 60 days before a Redemption Date,
the Company shall mail a notice of redemption by first-class mail, postage
prepaid, to each Holder of Notes to be redeemed. Once notice of redemption is
given, Notes called for redemption become due and payable on the Redemption Date
and at the Redemption Price, except for Notes which are converted in accordance
with the terms of this Indenture. Upon surrender to the Paying Agent, such Notes
shall be paid at the Redemption Price. If the Paying Agent holds, in accordance
with the terms hereof, at 11:00 a.m., New York City time, on the applicable
Redemption Date, cash sufficient to pay the Redemption Price of any Notes for
which notice of

                                      A-7
<PAGE>

redemption is given, then, on such Redemption Date, such Notes shall cease to be
outstanding and interest, Additional Amounts and Additional Interest, if any, on
such Notes shall cease to accrue, whether or not such Notes are delivered to the
Paying Agent, and the rights of the Holders in respect thereof shall terminate
(other than the right to receive the Redemption Price upon delivery of such
Notes).

6.    Purchase by the Company at the Option of the Holder on Specific Dates;
Purchase at the Option of the Holder Upon a Fundamental Change.

            Each Holder shall have the right, at the Holder's option, but
subject to the provisions of the Indenture, to require the Company to purchase
all of such Holder's Notes not theretofore called for redemption, or any portion
of the principal amount thereof that is equal to $1,000 or an integral multiple
thereof, on each of March 15, 2011, March 15, 2014 and March 15, 2019. The
Company shall be required to purchase such Notes at a purchase price in cash
(subject to the Company's right to elect to pay all or a portion of such
purchase price in shares of Common Stock, on the terms and subject to the
conditions set forth in Section 4.01 of the Indenture) equal to 100% of the
principal amount plus accrued and unpaid interest, Additional Amounts and
Additional Interest, if any, to, but excluding, the Purchase Date. To exercise
such right, a Holder shall deliver a Purchase Notice to the Paying Agent at any
time from the opening of business on the date that is 22 Business Days prior to
the relevant Purchase Date until the close of business on the second Business
Day prior to such Purchase Date.

            In the event that a Fundamental Change shall occur at any time prior
to the Stated Maturity, each Holder shall have the right, at the Holder's
option, but subject to the provisions of the Indenture, to require the Company
to purchase all of such Holder's Notes not theretofore called for redemption, or
any portion of the principal amount thereof that is equal to $1,000 or an
integral multiple thereof. The Company shall be required to purchase such Notes
at a purchase price in cash equal to 100% of the principal amount plus any
accrued and unpaid interest, Additional Amounts and Additional Interest, if any,
to, but excluding, the Fundamental Change Purchase Date. To exercise such right,
a Holder shall deliver a Fundamental Change Purchase Notice to the Paying Agent
at any time on or before the 20th Business Day after the date of the Company's
notice of the Fundamental Change (subject to extension to comply with applicable
law).

            Holders have the right to withdraw any Purchase Notice or
Fundamental Change Purchase Notice by delivering to the Paying Agent a written
notice of withdrawal in accordance with the provisions of the Indenture.

            If the Paying Agent holds, in accordance with the terms hereof, at
11:00 a.m., New York City time, on the Business Day immediately succeeding
applicable Purchase Date or Fundamental Change Purchase Date, cash or shares of
Common Stock (as applicable under the terms of the Indenture) sufficient to
irrevocably pay the Purchase Price or Fundamental Change Purchase Price, as the
case may be, of any Notes for which a Purchase Price or Fundamental Change
Purchase Notice, as the case may be, has been tendered and not withdrawn
pursuant to the Indenture, then, as of such Purchase Date or Fundamental Change
Purchase Date, as the case may be, such Notes shall cease to be outstanding and
interest, Additional Amounts and Additional Interest, if any, on such Notes
shall cease to accrue, whether or not such Notes are

                                      A-8
<PAGE>

delivered to the Paying Agent, and the rights of the Holders in respect thereof
shall terminate (other than the right to receive the Purchase Price or
Fundamental Change Purchase Price, as the case may be, upon delivery of such
Notes).

7.    Conversion.

            Subject to and in compliance with the provisions of the Indenture
(including, without limitation, the conditions to conversion of this Note set
forth in Section 12.1 thereof), the Holder of this Note is entitled, at such
Holder's option, to convert this Note (or any portion of the principal amount
hereof that is $1,000 or an integral multiple thereof), into fully paid and
non-assessable shares of Common Stock at the Conversion Rate in effect on the
date of conversion. The number of shares of Common Stock issuable upon
conversion of each $1,000 of principal amount of Notes is initially 51.3611
shares of Common Stock, and this Conversion Rate is subject to adjustment in
certain events as set forth in the Indenture.

            Upon conversion, the Company shall have the right to deliver, in
lieu of shares of Common Stock, cash or a combination of cash and shares of
Common Stock as provided in the Indenture. The Company shall notify Holders of
any event triggering the right to convert the Notes as specified in the
Indenture in accordance with the Indenture.

            On the first date the Notes become convertible under the above
circumstances, the Company shall notify Holders in writing of its Principal
Conversion Settlement Election. This notification once provided to a Holder on
the first conversion date, regardless of a Holder's decision to convert, is
irrevocable and legally binding with regard to any subsequent conversion of the
Notes. Until the Notes are surrendered for conversion, however, the Company
shall not be required to notify Holders of its method for settling its Excess
Amount Conversion Obligation.

            With respect to any conversion of this Note during a Registration
Default Period following satisfaction of any of the conditions to conversion
described in the Indenture (and during the prescribed time periods in respect
thereof), the Holder shall be entitled, subject to the Indenture, to 103% of the
number of shares of Common Stock that the Holder would have otherwise been
entitled to upon conversion in respect of the portion of the Conversion
Obligation that the Company settles in Common Stock.

            A Note in respect of which a Holder has delivered a Purchase Notice
or Fundamental Change Purchase Notice, as the case may be, exercising the right
of such Holder to require the Company to purchase such Note may be converted
only if such Purchase Notice or Fundamental Change Purchase Notice is withdrawn
in accordance with the terms of the Indenture.

            Except as described in Section 12.9 of the Indenture, the Company
will not make any payment in cash or Common Stock or other adjustment for
accrued and unpaid interest, Additional Amounts or Additional interest on any
Notes when they are converted. The Company's delivery to the Holder of the full
number of shares of Common Stock into which this Note is convertible (or, at the
Company's option, cash, or a combination of cash and Common Stock, in lieu
thereof as provided in the Indenture), together with any cash payment for such
Holder's fractional shares, shall be deemed to satisfy the Company's obligation
to pay the

                                      A-9
<PAGE>

principal amount of this Note and to satisfy its obligation to pay accrued and
unpaid interest, Additional Amounts and Additional Interest, if any through the
conversion date. As a result, accrued interest, Additional Amounts and
Additional Interest are deemed paid in full rather than cancelled, extinguished
or forfeited. Notwithstanding the foregoing, accrued interest, Additional
Amounts and Additional Interest, if any, will be payable in cash upon any
conversion of Notes made concurrently with or after acceleration of the Notes
following an Event of Default.

            Before any Holder shall be entitled to convert any Notes into Common
Stock, such Holder shall, in the case of Global Securities, comply with the
Applicable Procedures of the Depositary in effect at that time, and in the case
of Certificated Securities, surrender such Securities, duly endorsed to the
Company or in blank if required by the Conversion Agent, at the office of the
Conversion Agent, and shall give written notice to the Company at said office or
place in the form of the Conversion Notice attached to this Note that such
Holder elects to convert the same and shall state in writing therein the
principal amount of Notes to be converted (in whole or in part so long as the
principal amount to be converted is in multiples of $1,000) and the name or
names (with addresses) in which such Holder wishes the certificate or
certificates for Common Stock to be issued. Before any such conversion, a Holder
also shall pay all funds required, if any, relating to interest, Additional
Amounts or Additional Interest, if any, on the Notes, as provided in Section
12.9 of the Indenture, and all taxes or duties, if any, as provided in Section
12.8 of the Indenture.

            If the Company (i) reclassifies or changes the Common Stock, (ii) is
a party to a consolidation, merger, statutory share exchange or combination or
(iii) sells or conveys all or substantially all of its properties and assets to
any Person, the right to convert a Note into shares of Common Stock may be
changed into a right to convert it into securities, cash or other property of
the Company or the successor or purchasing Person, in each case in accordance
with Section 12.4 of the Indenture.

8.    Denominations; Transfer; Exchange.

            The Notes shall be issued in fully registered form, without coupons,
in denominations of $1,000 of principal amount and integral multiples thereof. A
Holder may transfer or exchange Notes in accordance with the Indenture. The
Registrar may require a Holder, among other things, to furnish appropriate
endorsements and transfer documents and to pay any taxes and fees required by
law or permitted by the Indenture. Neither the Company, the Registrar nor the
Trustee shall be required to exchange or register a transfer of (i) any Notes
selected for redemption (except, in the case of Notes to be redeemed in part,
the portion thereof not to be redeemed), or (ii) any Notes in respect of which a
Purchase Notice or a Fundamental Change Purchase Notice has been given and not
withdrawn by the Holder thereof in accordance with the terms of the Indenture
(except, in the case of Notes to be repurchased in part, the portion thereof not
to be repurchased), or (iii) any Notes surrendered for conversion (except, in
the case of Notes to be converted in part, the portion thereof not to be
converted).

9.    Persons Deemed Owners.

            The registered holder of this Note may be treated as the owner of
this Note for all purposes.

                                      A-10
<PAGE>

10.   Unclaimed Money or Securities.

            The Trustee, the Paying Agent and the Conversion Agent shall return
to the Company upon written request any cash or securities held by them for the
payment of any amount with respect to the Notes that remains unclaimed for two
years, subject to applicable unclaimed property law. After return to the
Company, Holders entitled to the money or securities must look to the Company
for payment as general creditors unless an applicable abandoned property law
designates another person.

11.   Amendment; Waiver.

            Subject to certain exceptions set forth in the Indenture, (i) the
Indenture or the Notes may be amended with the written consent or affirmative
vote of the Holders of at least a majority in aggregate principal amount of the
outstanding Notes and (ii) certain Defaults may be waived with the written
consent or affirmative vote of the Holders of a majority in aggregate principal
amount of the outstanding Notes.

            The Company and the Trustee may amend the Indenture or the Notes
without the consent of any Holder to (a) add to the covenants of the Company for
the benefit of the Holders of Notes; (b) surrender any right or power herein
conferred upon the Company; (c) provide for conversion rights of Holders of
Notes if any reclassification or change of the Common Stock or any
consolidation, merger or disposition of all or substantially all of the
Company's properties and assets occurs; (d) provide for the assumption of the
Company's obligations to the Holders of Notes in the case of a merger,
consolidation, conveyance, transfer, sale, lease or other disposition pursuant
to Article VII of the Indenture; (e) increase the Conversion Rate; provided,
however, that such increase in the Conversion Rate shall not adversely affect
the interests of the Holders of Notes (after taking into account tax and other
consequences of such increase); (f) comply with the requirements of the SEC in
order to effect or maintain the qualification of the Indenture under the TIA;
(g) make any changes or modifications necessary in connection with the
registration of the Notes under the Securities Act as contemplated in the
Registration Rights Agreement; provided, however, that such action pursuant to
this clause (g) does not, in the good faith opinion of the Board of Directors
(as evidenced by a Board Resolution), adversely affect the interests of the
Holders of Notes in any material respect; (h) cure any ambiguity, correct or
supplement any provision in the Indenture which may be inconsistent with any
other provision therein or which is otherwise defective, or to make any other
provisions with respect to matters or questions arising under the Indenture
which the Company may deem necessary or desirable and which shall not be
inconsistent with the provisions of the Indenture; provided, however, that such
action pursuant to this clause (h) does not, in the good faith opinion of the
Board of Directors (as evidenced by a Board Resolution), adversely affect the
interests of the Holders of Notes in any material respect; (i) to evidence the
succession of another Person to the Company or any other obligor upon the Notes,
and the assumption by any such successor of the covenants of the Company or such
obligor in the Indenture and in the Notes, in each case in compliance with the
provisions of the Indenture; (j) to evidence and provide the acceptance of the
appointment of a successor Trustee and (k) to require the Company to settle (i)
its obligation to purchase Notes under ARTICLE IV of the Indenture in cash or
(ii) its Conversion Obligation in cash with respect to the principal amount of
Notes surrendered for conversion.

                                      A-11
<PAGE>

12.   Defaults and Remedies.

            If any Event of Default, other than as a result of certain events of
bankruptcy, insolvency or reorganization of the Company as specified in the
Indenture, occurs and is continuing, the principal amount of all the Notes may
be declared due and payable in the manner and with the effect provided in the
Indenture. If an Event of Default occurs as a result of certain events of
bankruptcy, insolvency or reorganization of the Company as provided in the
Indenture, the principal amount of all the Notes shall become due and payable
immediately without any declaration or other act on the part of the Trustee or
any Holder, all as and to the extent provided in the Indenture.

13.   Trustee Dealings with the Company.

            Subject to certain limitations imposed by the TIA, the Trustee under
the Indenture, in its individual or any other capacity, may become the owner or
pledgee of Notes and may otherwise deal with and collect obligations owed to it
by the Company or its Affiliates and may otherwise deal with the Company or its
Affiliates with the same rights it would have if it were not Trustee.

14.   Calculations in Respect of Notes.

            The Company or its agents shall be responsible for making all
calculations called for under ARTICLE XII and ARTICLE XIII of the Indenture,
including, but not limited to, determination of the Closing Sale Price of
Applicable Stock, the Note Price, the number of shares of Common Stock or other
Applicable Stock and/or the amount of cash issuable or payable upon conversion
and the amounts of interest, Additional Amounts and Additional Interest, if any,
on the Notes. Any calculations made in good faith and without manifest error
shall be final and binding on Holders of the Notes. The Company or its agents
shall be required to deliver to the Trustee a schedule of its calculations and
the Trustee shall be entitled to conclusively rely upon the accuracy of such
calculations without independent verification.

15.   No Recourse Against Others.

            No recourse under or upon any obligation, covenant or agreement
contained in this Indenture or in any Note, or because of any indebtedness
evidenced thereby, shall be had against any incorporator, as such, or against
any past, present or future stockholder, officer or director, as such, of the
Company or of any successor, either directly or through the Company or any
successor, under any rule of law, statute or constitutional provision or by the
enforcement of any assessment or by any legal or equitable proceeding or
otherwise, all such liability being expressly waived and released by the
acceptance of the Notes by the Holders and as part of the consideration for the
issue of the Notes.

16.   Authentication.

            This Note shall not be valid or obligatory for any purpose until an
authorized signatory of the Trustee (or a duly authorized authentication agent)
signs the Trustee's Certificate of Authentication on the other side of this
Note.

                                      A-12
<PAGE>

17.   Abbreviations.

            Customary abbreviations may be used in the name of a Holder or an
assignee, such as TEN COM (=tenants in common), TEN ENT (=tenants by the
entireties), JT TEN (=joint tenants with right of survivorship and not as
tenants in common), CUST (=custodian), and U/G/M/A (=Uniform Gift to Minors
Act).

18.   INDENTURE TO CONTROL; GOVERNING LAW.

            IN THE CASE OF ANY CONFLICT BETWEEN THE PROVISIONS OF THIS NOTE AND
THE INDENTURE, TO THE EXTENT PERMITTED BY APPLICABLE LAW, THE PROVISIONS OF THE
INDENTURE SHALL CONTROL. THE INDENTURE AND THIS NOTE SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK.

19.   Registration Rights.

            The Holders of the Notes are entitled to the benefits of a
Registration Rights Agreement, dated March 12, 2004, among the Company, Bear,
Stearns & Co. Inc., CIBC World Markets Corp. and Credit Lyonnais Securities
(USA), Inc., as amended, modified or supplemented in accordance therewith,
including the receipt of Additional Interest upon a Registration Default (as
defined in such agreement).

20.   Copies of Indenture and Registration Rights Agreement.

            The Company shall furnish to any Holder upon written request and
without charge a copy of the Indenture and a copy of the Registration Rights
Agreement. Requests may be made to:

            WILLBROS GROUP, INC.
            c/o Willbros USA, Inc.
            4400 Post Oak Parkway
            Suite 1000
            Houston, Texas 77027
            Attention: Chief Financial Officer
            Facsimile No.: (713) 403-8010

                                      A-13
<PAGE>

                                ASSIGNMENT FORM

To assign this Note, fill in the form below:

I or we assign and transfer this Note to

_______________________________________________________________________________
                  (Insert assignee's soc. sec. or tax ID no.)

_______________________________________________________________________________
             (Print or type assignee's name, address and zip code)

and irrevocably appoint ________________________________________________________
agent to transfer this Note on the books of the Company. The agent may
substitute another to act for him.

                                    Your Signature(s):

Date:_______________________         ___________________________________________
                                    (Sign exactly as your name(s) appears on the
                                    other side of this Note)

Signature Guaranteed

________________________________
Participant in a Recognized Signature
Guarantee Medallion Program

By:________________________________
   Authorized Signatory

                                      A-14
<PAGE>

                       OPTION OF HOLDER TO ELECT PURCHASE

If you wish to have this Note purchased by the Company pursuant to ARTICLE IV
(Purchase at the Option of Holders on Specific Dates) or ARTICLE V (Purchase at
the Option of Holders Upon a Fundamental Change) of the Indenture, check the
box: ARTICLE IV [ ] ARTICLE V [ ].

If this Note is to be purchased by the Company pursuant to ARTICLE IV of the
Indenture, check the box for the applicable Purchase Date: March 15, 2011 [ ]
March 15, 2014 [ ] March 15, 2019 [ ].

If you wish to have a portion of this Note purchased by the Company pursuant to
ARTICLE IV or ARTICLE V of the Indenture, as applicable, state the amount (in
principal amount): $ ______________.

If certificated, the serial numbers of the Notes to be delivered for purchase
are:

______________.

            Any purchase of Notes pursuant hereto shall be pursuant to the terms
and conditions specified in the Indenture.

                                    Your Signature(s):

Date:_______________________        ____________________________________________
                                    (Sign exactly as your name(s) appears on the
                                    other side of this Note)

Signature Guaranteed

________________________________
Participant in a Recognized Signature
Guarantee Medallion Program

By:___________________________________
   Authorized Signatory

                                      A-15
<PAGE>

                               CONVERSION NOTICE

To convert this Note into Common Stock of the Company (or cash or a combination
of Common Stock and cash, if the Company so elects), check the box [ ].

To convert only part of this Note, state the principal amount to be converted
(which must be $1,000 or an integral multiple thereof):____________________.

If you want the stock certificate made out in another person's name fill in the
form below:

_______________________________________________________________________________
              (Insert the other person's soc. sec. or tax ID no.)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________
         (Print or type the other person's name, address and zip code)

                                        Your Signature(s):

Date: _______________________           ________________________________________
                                        (Sign exactly as your name(s) appears on
                                        the other side of this Note) Signature
                                        Guaranteed

________________________________

Participant in a Recognized Signature
Guarantee Medallion Program

By:__________________________________
   Authorized Signatory

                                      A-16
<PAGE>

                            TRANSFER CERTIFICATE(4)

                   Re: 2.75% Convertible Senior Notes due 2024
              (the "Notes") of Willbros Group, Inc. (the "Company")

            This certificate relates to $_______ principal amount of Notes owned
in (check applicable box)

            [ ] book-entry    [ ] definitive form by__________the "Transferor").

            The Transferor has requested a Registrar or the Trustee to exchange
or register the transfer of such Notes.

            In connection with such request and in respect of each such Note,
the Transferor does hereby certify that the Transferor is familiar with transfer
restrictions relating to the Notes as provided in Section 2.6 and Section 2.12
of the Indenture dated as of March 12, 2004 between the Company and JPMorgan
Chase Bank, as Trustee (the "Indenture"), and the transfer of such Note is being
made pursuant to an effective registration statement under the Securities Act of
1933, as amended (the "Securities Act") (check applicable box) or the transfer
or exchange, as the case may be, of such Note does not require registration
under the Securities Act because (check applicable box):

            [ ]   Such Note is being acquired for the Transferor's own account,
                  without transfer; or

            [ ]   Such Note is being transferred to the Company or a Subsidiary;
                  or

            [ ]   Such Note is being transferred to a person that the Transferor
                  reasonably believes is a "qualified institutional buyer," as
                  defined in, and in compliance with, Rule 144A under the
                  Securities Act; or

            [ ]   Such Note is being transferred pursuant to the exemption from
                  the registration requirements of the Securities Act under Rule
                  144 (or any successor thereto) ("Rule 144") under the
                  Securities Act; or

            [ ]   Such Note is being transferred pursuant to an effective
                  registration statement under the Securities Act; or

            [ ]   Such Note is being transferred pursuant to an exemption from
                  the registration requirements of the Securities Act to an
                  institutional investor that is an "accredited investor" (as
                  defined in Rule 501(a)(1), (2), (3) or (7) of Regulation D
                  under the Securities Act) that, prior to the transfer,

------------------
(4) This certificate should only be included if this Security is a Transfer
Restricted Security.

                                      A-17
<PAGE>

                  furnishes to the Trustee such certifications and opinion of
                  counsel required by the Company or the Trustee.

            The Transferor acknowledges and agrees that, if the transferee will
hold any such Notes in the form of beneficial interests in a global Note that is
a "restricted security" within the meaning of Rule 144 under the Securities Act,
then such transfer can be made only pursuant to Rule 144A under the Securities
Act and such transferee must be a "qualified institutional buyer," as defined in
Rule 144A, or an institutional investor that is an "accredited investor" (as
defined in Rule 501(a)(1), (2), (3) or (7) of Regulation D under the Securities
Act).

                                       _________________________________________
            Date:                             Signature(s) of Transferor

(If the registered owner is a corporation, partnership or fiduciary, the title
of the person signing on behalf of such registered owner must be stated.)

Signature Guaranteed

_____________________________________
Participant in a Recognized Signature
Guarantee Medallion Program

By:__________________________________
   Authorized Signatory

                                      A-18
<PAGE>

                                   EXHIBIT B

                    [FORM OF CERTIFICATE TO BE DELIVERED BY
                    TRANSFEREE IN CONNECTION WITH TRANSFERS
                     TO INSTITUTIONAL ACCREDITED INVESTORS]

                                   [Date]

JPMorgan Chase Bank, as Trustee
4 New York Plaza, 15th Floor
New York, New York 10004
Attention: Corporate Trust Administration

                           Re: Willbros Group, Inc.

Ladies and Gentlemen:

            In connection with the undersigned's proposed purchase of
$____________ aggregate principal amount of 2.75% Convertible Senior Notes due
2024 (the "Notes") of Willbros Group, Inc. (the "Company") or _____________
shares of Common Stock of the Company issued upon conversion of the Notes, par
value $.05 per share (the "Common Stock," and together with the Notes, the
"Securities"), the undersigned confirms, represents and warrants that:

                  (1) The undersigned is an institutional "accredited investor"
            within the meaning of Rule 501(a)(1), (2), (3) or (7) under the
            Securities Act of 1933, as amended (the "Securities Act") (an
            "Institutional Accredited Investor").

                  (2) (A) Any purchase of the Securities by the undersigned will
            be for the undersigned's own account or for the account of one or
            more other Institutional Accredited Investors or as fiduciary for
            the account of one or more trusts, each of which is an "accredited
            investor" within the meaning of Rule 501(a)(7) under the Securities
            Act and for each of which the undersigned exercises sole investment
            discretion or (B) the undersigned is a "bank", within the meaning of
            Section 3(a)(2) of the Securities Act, or a "savings and loan
            association" or other institution described in Section 3(a)(5)(A) of
            the Securities Act that is acquiring the Securities as fiduciary for
            the account of one or more institutions for which the undersigned
            exercises sold investment discretion.

                  (3) The undersigned has such knowledge and experience in
            financial and business matters that the undersigned is capable of
            evaluating the merits and risks of its investment in the Securities,
            and the undersigned and any accounts for which it is acting is each
            able to bear the economic risk of its or their investment.

                  (4) The undersigned has been given an opportunity to ask
            questions and receive answers concerning the terms and conditions of
            the Securities and to obtain any additional information which the
            Company possesses or can acquire

                                      B-1
<PAGE>

            without reasonable effort or expense that is necessary to verify the
            accuracy of the information furnished.

                  (5) The undersigned is not acquiring the Securities with a
            view to distribution thereof or with any present intention of
            offering or selling any Securities, except as permitted below;
            provided that the disposition of the undersigned's property and the
            property of any accounts for which the undersigned is acting as
            fiduciary will remain at all times within the undersigned's control.

                  (6) The undersigned understands that the Securities have not
            been registered under the Securities Act or any applicable state
            securities laws.

                  (7) The undersigned agrees, on its own behalf and on behalf of
            each account for which the undersigned acquires any Securities, that
            if in the future the undersigned decides to resell or otherwise
            transfer such Securities within two years after the latest date of
            the original issuance of the Notes, such Securities may be resold or
            otherwise transferred only:

                  (A)   to the Company or any subsidiary thereof;

                  (B)   with respect to Notes only, to a person which is a
            "qualified institutional buyer" (as defined in Rule 144A under the
            Securities Act) and otherwise in compliance with Rule 144A under the
            Securities Act;

                  (C)   pursuant to the exemption from registration provided by
            Rule 144 under the Securities Act (if available);

                  (D)   pursuant to an exemption from the registration
            requirements under the Securities Act to a person whom the purchaser
            reasonably believes is an Institutional Accredited Investor that
            prior to such transfer, furnishes to you (and the Trustee or the
            Transfer Agent, as the case may be) a signed letter substantially in
            the form of this letter, a transfer certificate substantially in the
            form provided in the Indenture and an opinion of counsel; or

                  (E)   pursuant to a registration statement which has been
            declared effective under the Securities Act and continues to be
            effective at the time of such transfer.

            The undersigned further agrees to provide to any person purchasing
            any of the Securities from us (other than a purchaser described in
            clause (A), (C) or (E) above) a written notice advising such
            purchaser that resales of the Securities are restricted as stated
            herein.

                  (8) The undersigned understands that, on any proposed resale
            of any Securities, the undersigned shall be required to furnish to
            the Trustee or the Transfer Agent, as the case may be, and the
            Company such certifications, legal opinions and other information as
            you and the Company may reasonably require

                                      B-2
<PAGE>

            to confirm that the proposed sale complies with the foregoing
            restrictions. The undersigned further understands that the
            Securities purchased by the undersigned will bear a legend to the
            foregoing effect.

            Each of the Company, the Trustee or the Transfer Agent, as the case
may be, and the initial purchasers of the Securities is entitled to rely upon
this letter and are irrevocably authorized to produce this letter or a copy
hereof to any interested party in any administrative or legal proceedings or
official inquiry with respect to the matters covered hereby.

                                      Very truly yours,

                                      By:_____________________________
                                         Name:
                                         Title:
                                         Address:

                                      B-3
<PAGE>

                                                                               1

                                   EXHIBIT C

                        [FORM OF RESTRICTIVE LEGEND FOR
                      COMMON STOCK ISSUED UPON CONVERSION]

            THE SECURITY EVIDENCED BY THIS CERTIFICATE HAS NOT BEEN REGISTERED
UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "SECURITIES ACT OF 1933"), OR
ANY STATE SECURITIES LAWS, AND MAY NOT BE OFFERED OR SOLD EXCEPT AS SET FORTH IN
THE FOLLOWING SENTENCE. BY ACQUISITION HEREOF, THE HOLDER:

                  (1)   REPRESENTS THAT (A) IT IS A "QUALIFIED INSTITUTIONAL
      BUYER" AS DEFINED IN RULE 144A UNDER THE SECURITIES ACT OF 1933 OR (B) IT
      IS AN INSTITUTIONAL INVESTOR THAT IS AN "ACCREDITED INVESTOR" AS DEFINED
      IN RULE 501(a)(1), (2), (3), OR (7) UNDER THE SECURITIES ACT (AN
      "INSTITUTIONAL ACCREDITED INVESTOR");

                  (2)   AGREES THAT IT SHALL NOT, WITHIN TWO YEARS AFTER THE
      ORIGINAL ISSUANCE OF THE SECURITY UPON THE CONVERSION OF WHICH THE SHARES
      OF COMMON STOCK EVIDENCED HEREBY WERE ISSUED, RESELL OR OTHERWISE TRANSFER
      THE SECURITY EVIDENCED HEREBY EXCEPT (A) TO THE WILLBROS GROUP, INC. OR
      ANY SUBSIDIARY THEREOF, (B) PURSUANT TO THE EXEMPTION FROM THE
      REGISTRATION REQUIREMENTS OF THE SECURITIES ACT OF 1933 PROVIDED BY RULE
      144 UNDER THE SECURITIES ACT (IF AVAILABLE), (C) TO THE EXTENT PERMITTED
      BY APPLICABLE LAW, TO A PERSON THAT THE HOLDER REASONABLY BELIEVES IS A
      "QUALIFIED INSTITUTIONAL BUYER" AS DEFINED IN, AND IN COMPLIANCE WITH,
      RULE 144A UNDER THE SECURITIES ACT OF 1933, (D) PURSUANT TO AN EXEMPTION
      FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT OF 1933 (IF
      AVAILABLE) TO AN INSTITUTIONAL ACCREDITED INVESTOR THAT PRIOR TO SUCH
      TRANSFER, FURNISHES TO MELLON INVESTOR SERVICES LLC, AS TRANSFER AGENT (OR
      ANY SUCCESSOR TRANSFER AGENT, AS APPLICABLE), SUCH CERTIFICATIONS AND
      OPINION OF COUNSEL REQUIRED BY THE COMPANY OR TRANSFER AGENT OR (E)
      PURSUANT TO A REGISTRATION STATEMENT THAT HAS BEEN DECLARED EFFECTIVE
      UNDER THE SECURITIES ACT OF 1933 AND THAT CONTINUES TO BE EFFECTIVE AT THE
      TIME OF SUCH TRANSFER; AND

                  (3)   AGREES THAT IT SHALL DELIVER TO EACH PERSON TO WHOM THE
      SECURITY EVIDENCED HEREBY IS TRANSFERRED (OTHER THAN A TRANSFER PURSUANT
      TO CLAUSE 2(A), 2(B) OR 2(E) ABOVE), A NOTICE SUBSTANTIALLY TO THE EFFECT
      OF THIS LEGEND.

      THE HOLDER OF THIS SECURITY IS ENTITLED TO THE BENEFITS OF A REGISTRATION
      RIGHTS AGREEMENT (AS SUCH TERM IS DEFINED IN THE

                                      C-1
<PAGE>

                                                                               2

      INDENTURE REFERRED TO ON THE REVERSE HEREOF) AND, BY ITS ACCEPTANCE
      HEREOF, AGREES TO BE BOUND BY AND TO COMPLY WITH THE PROVISIONS OF SUCH
      REGISTRATION RIGHTS AGREEMENT.

                                      C-2