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                                                                     EXHIBIT 4.5


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                              WILLBROS GROUP, INC.

                                       AND

                      [                                  ]
                       ----------------------------------
                                   AS TRUSTEE

                                    INDENTURE

                          DATED AS OF           , 200
                                      ----------     --

                          SUBORDINATED DEBT SECURITIES



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                                TABLE OF CONTENTS

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                                               ARTICLE I
                                   DEFINITIONS AND OTHER PROVISIONS
                                        OF GENERAL APPLICATION

     SECTION 1.1    DEFINITIONS.......................................................................1
     SECTION 1.2    COMPLIANCE CERTIFICATES AND OPINIONS.............................................11
     SECTION 1.3    FORM OF DOCUMENTS DELIVERED TO TRUSTEE...........................................12
     SECTION 1.4    ACTS OF HOLDERS; RECORD DATES....................................................13
     SECTION 1.5    NOTICES, ETC., TO TRUSTEE AND COMPANY............................................15
     SECTION 1.6    NOTICE TO HOLDERS; WAIVER........................................................16
     SECTION 1.7    CONFLICT WITH TRUST INDENTURE ACT................................................16
     SECTION 1.8    EFFECT OF HEADINGS AND TABLE OF CONTENTS.........................................16
     SECTION 1.9    SUCCESSORS AND ASSIGNS...........................................................16
     SECTION 1.10   SEPARABILITY CLAUSE..............................................................17
     SECTION 1.11   BENEFITS OF INDENTURE............................................................17
     SECTION 1.12   GOVERNING LAW....................................................................17
     SECTION 1.13   LEGAL HOLIDAYS...................................................................17
     SECTION 1.14   INDENTURE AND SECURITIES SOLELY CORPORATE OBLIGATIONS............................17
     SECTION 1.15   INDENTURE MAY BE EXECUTED IN COUNTERPARTS........................................18

                                              ARTICLE II
                                            SECURITY FORMS

     SECTION 2.1   FORMS GENERALLY...................................................................18
     SECTION 2.2   FORM OF LEGEND FOR GLOBAL SECURITIES..............................................18
     SECTION 2.3   FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION...................................19
     SECTION 2.4   FORM OF CONVERSION NOTICE.........................................................19


                                              ARTICLE III
                                            THE SECURITIES

     SECTION 3.1   AMOUNT UNLIMITED; ISSUABLE IN SERIES..............................................21
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     SECTION 3.2    DENOMINATIONS....................................................................25
     SECTION 3.3    EXECUTION, AUTHENTICATION, DELIVERY AND DATING...................................25
     SECTION 3.4    TEMPORARY SECURITIES.............................................................27
     SECTION 3.5    REGISTRATION; REGISTRATION OF TRANSFER AND EXCHANGE..............................27
     SECTION 3.6    MUTILATED, DESTROYED, LOST AND STOLEN SECURITIES.................................29
     SECTION 3.7    PAYMENT OF INTEREST; INTEREST RIGHTS PRESERVED...................................30
     SECTION 3.8    PERSONS DEEMED OWNERS............................................................32
     SECTION 3.9    CANCELLATION.....................................................................32
     SECTION 3.10   COMPUTATION OF INTEREST..........................................................33

                                              ARTICLE IV
                                      SATISFACTION AND DISCHARGE

     SECTION 4.1    SATISFACTION AND DISCHARGE OF INDENTURE..........................................33
     SECTION 4.2    APPLICATION OF TRUST MONEY.......................................................34

                                               ARTICLE V
                                               REMEDIES

     SECTION 5.1    EVENTS OF DEFAULT................................................................35
     SECTION 5.2    ACCELERATION OF MATURITY; RESCISSION AND ANNULMENT...............................36
     SECTION 5.3    COLLECTION OF INDEBTEDNESS AND SUITS FOR ENFORCEMENT BY TRUSTEE..................38
     SECTION 5.4    TRUSTEE MAY FILE PROOFS OF CLAIM.................................................38
     SECTION 5.5    TRUSTEE MAY ENFORCE CLAIMS WITHOUT POSSESSION OF SECURITIES......................39
     SECTION 5.6    APPLICATION OF MONEY COLLECTED...................................................39
     SECTION 5.7    LIMITATION ON SUITS..............................................................40
     SECTION 5.8    UNCONDITIONAL RIGHT OF HOLDERS TO RECEIVE PRINCIPAL, PREMIUM AND
                        INTEREST AND TO CONVERT......................................................41
     SECTION 5.9    RESTORATION OF RIGHTS AND REMEDIES...............................................41
     SECTION 5.10   RIGHTS AND REMEDIES CUMULATIVE...................................................41
     SECTION 5.11   DELAY OR OMISSION NOT WAIVER.....................................................41
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     SECTION 5.12   CONTROL BY HOLDERS...............................................................42
     SECTION 5.13   WAIVER OF PAST DEFAULTS..........................................................42
     SECTION 5.14   UNDERTAKING FOR COSTS............................................................43
     SECTION 5.15   WAIVER OF USURY, STAY OR EXTENSION LAWS..........................................43

                                              ARTICLE VI
                                              THE TRUSTEE

     SECTION 6.1    CERTAIN DUTIES AND RESPONSIBILITIES..............................................43
     SECTION 6.2    NOTICE OF DEFAULTS...............................................................44
     SECTION 6.3    CERTAIN RIGHTS OF TRUSTEE........................................................44
     SECTION 6.4    NOT RESPONSIBLE FOR RECITALS OR ISSUANCE OF SECURITIES...........................45
     SECTION 6.5    MAY HOLD SECURITIES AND ACT AS TRUSTEE UNDER OTHER INDENTURES....................45
     SECTION 6.6    MONEY HELD IN TRUST..............................................................46
     SECTION 6.7    COMPENSATION AND REIMBURSEMENT...................................................46
     SECTION 6.8    CONFLICTING INTERESTS............................................................46
     SECTION 6.9    CORPORATE TRUSTEE REQUIRED; ELIGIBILITY..........................................47
     SECTION 6.10   RESIGNATION AND REMOVAL; APPOINTMENT OF SUCCESSOR................................47
     SECTION 6.11   ACCEPTANCE OF APPOINTMENT BY SUCCESSOR...........................................49
     SECTION 6.12   MERGER, CONVERSION, CONSOLIDATION OR SUCCESSION TO BUSINESS......................50
     SECTION 6.13   PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY................................50
     SECTION 6.14   APPOINTMENT OF AUTHENTICATING AGENT..............................................51


                                              ARTICLE VII
                           HOLDERS' LISTS AND REPORTS BY TRUSTEE AND COMPANY

     SECTION 7.1    COMPANY TO FURNISH TRUSTEE NAMES AND ADDRESSES OF HOLDERS........................53
     SECTION 7.2    PRESERVATION OF INFORMATION; COMMUNICATIONS TO HOLDERS...........................53
     SECTION 7.3    REPORTS BY TRUSTEE...............................................................54
     SECTION 7.4    REPORTS BY COMPANY...............................................................54
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                                             ARTICLE VIII
                         CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE

     SECTION 8.1    COMPANY MAY CONSOLIDATE, ETC., ONLY ON CERTAIN TERMS.............................54
     SECTION 8.2    SUCCESSOR SUBSTITUTED............................................................55

                                              ARTICLE IX
                                        SUPPLEMENTAL INDENTURES

     SECTION 9.1    SUPPLEMENTAL INDENTURES WITHOUT CONSENT OF HOLDERS...............................56
     SECTION 9.2    SUPPLEMENTAL INDENTURES WITH CONSENT OF HOLDERS. ................................58
     SECTION 9.3    EXECUTION OF SUPPLEMENTAL INDENTURES.............................................59
     SECTION 9.4    EFFECT OF SUPPLEMENTAL INDENTURES................................................59
     SECTION 9.5    CONFORMITY WITH TRUST INDENTURE ACT..............................................60
     SECTION 9.6    REFERENCE IN SECURITIES TO SUPPLEMENTAL INDENTURES...............................60
     SECTION 9.7    SUBORDINATION UNIMPAIRED.........................................................60

                                               ARTICLE X
                                               COVENANTS

     SECTION 10.1   PAYMENT OF PRINCIPAL, PREMIUM AND INTEREST.......................................60
     SECTION 10.2   MAINTENANCE OF OFFICE OR AGENCY..................................................60
     SECTION 10.3   MONEY FOR SECURITIES PAYMENTS TO BE HELD IN TRUST................................61
     SECTION 10.4   STATEMENT BY OFFICERS AS TO DEFAULT..............................................62
     SECTION 10.5   EXISTENCE........................................................................63
     SECTION 10.6   WAIVER OF CERTAIN COVENANTS......................................................63

                                              ARTICLE XI
                                       REDEMPTION OF SECURITIES

     SECTION 11.1   APPLICABILITY OF ARTICLE.........................................................63
     SECTION 11.2   ELECTION TO REDEEM; NOTICE TO TRUSTEE............................................63
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     SECTION 11.3   SELECTION BY TRUSTEE OF SECURITIES TO BE REDEEMED................................64
     SECTION 11.4   NOTICE OF REDEMPTION.............................................................65
     SECTION 11.5   DEPOSIT OF REDEMPTION PRICE......................................................66
     SECTION 11.6   SECURITIES PAYABLE ON REDEMPTION DATE............................................66
     SECTION 11.7   SECURITIES REDEEMED IN PART......................................................66

                                              ARTICLE XII
                                             SINKING FUNDS

     SECTION 12.1   APPLICABILITY OF ARTICLE.........................................................67
     SECTION 12.2   SATISFACTION OF SINKING FUND PAYMENTS WITH SECURITIES............................67
     SECTION 12.3   REDEMPTION OF SECURITIES FOR SINKING FUND........................................68

                                              ARTICLE XIII
                                  DEFEASANCE AND COVENANT DEFEASANCE

     SECTION 13.1   COMPANY'S OPTION TO EFFECT DEFEASANCE OR COVENANT DEFEASANCE.....................68
     SECTION 13.2   DEFEASANCE AND DISCHARGE.........................................................68
     SECTION 13.3   COVENANT DEFEASANCE..............................................................69
     SECTION 13.4   CONDITIONS TO DEFEASANCE OR COVENANT DEFEASANCE..................................70
     SECTION 13.5   DEPOSITED MONEY AND U.S. GOVERNMENT OBLIGATIONS TO BE HELD IN TRUST;
                        MISCELLANEOUS PROVISIONS.....................................................73
     SECTION 13.6   REINSTATEMENT....................................................................73


                                              ARTICLE XIV
                                       CONVERSION OF SECURITIES

     SECTION 14.1   APPLICABILITY OF ARTICLE.........................................................74
     SECTION 14.2   EXERCISE OF CONVERSION PRIVILEGE.................................................74
     SECTION 14.3   NO FRACTIONAL SHARES.............................................................75
     SECTION 14.4   ADJUSTMENT OF CONVERSION PRICE...................................................76
     SECTION 14.5   NOTICE OF CERTAIN CORPORATE ACTIONS..............................................76
     SECTION 14.6   RESERVATION OF SHARES OF COMMON STOCK............................................77
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     SECTION 14.7    PAYMENT OF CERTAIN TAXES UPON CONVERSION........................................78
     SECTION 14.8    NONASSESSABILITY................................................................78
     SECTION 14.9    PROVISION IN CASE OF CONSOLIDATION, MERGER OR SALE OF ASSETS....................78
     SECTION 14.10   DUTIES OF TRUSTEE REGARDING CONVERSION..........................................79
     SECTION 14.11   REPAYMENT OF CERTAIN FUNDS UPON CONVERSION......................................80

                                              ARTICLE XV
                                      SUBORDINATION OF SECURITIES

     SECTION 15.1    AGREEMENT OF SUBORDINATION......................................................80
     SECTION 15.2    PAYMENTS TO HOLDERS.............................................................81
     SECTION 15.3    SUBROGATION OF SECURITIES.......................................................84
     SECTION 15.4    AUTHORIZATION TO EFFECT SUBORDINATION...........................................85
     SECTION 15.5    NOTICE TO TRUSTEE...............................................................85
     SECTION 15.6    TRUSTEE'S RELATION TO SENIOR INDEBTEDNESS.......................................86
     SECTION 15.7    NO IMPAIRMENT OF SUBORDINATION..................................................87
     SECTION 15.8    CERTAIN CONVERSIONS DEEMED PAYMENT..............................................87
     SECTION 15.9    ARTICLE APPLICABLE TO PAYING AGENTS.............................................87
     SECTION 15.10   SENIOR INDEBTEDNESS ENTITLED TO RELY............................................88
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                  INDENTURE, dated as of ___________, 200__, between Willbros
Group, Inc., a corporation duly organized and existing under the laws of the
Republic of Panama (herein called the "Company"), having its principal executive
office at Plaza Bancomer Building, 50th Street, 8th Floor, Apartado 6307, Panama
5, Republic of Panama, and [___________________], as Trustee (herein called the
"Trustee").

                                  WITNESSETH:

                  WHEREAS, the Company has duly authorized the execution and
delivery of this Indenture to provide for the issuance from time to time of its
unsecured debentures, notes or other evidences of indebtedness (herein called
the "Securities"), to be issued in one or more series as provided in this
Indenture; and

                  WHEREAS, all things necessary to make this Indenture a valid
agreement of the Company, in accordance with its terms, have been done;

                  NOW, THEREFORE, in consideration of the premises and the
purchase of the Securities by the Holders thereof, it is mutually covenanted and
agreed, for the equal and proportionate benefit of all Holders of the Securities
or of series thereof appertaining, as follows:


                                    ARTICLE I

                        DEFINITIONS AND OTHER PROVISIONS
                             OF GENERAL APPLICATION

SECTION 1.1 DEFINITIONS.

                  For all purposes of this Indenture, except as otherwise
expressly provided or unless the context otherwise requires:

                           (1) the terms defined in this Article have the
         meanings assigned to them in this Article and include the plural as
         well as the singular;


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                           (2) all other terms used herein which are defined in
         the Trust Indenture Act, either directly or by reference therein, have
         the meanings assigned to them therein;

                           (3) all accounting terms not otherwise defined herein
         have the meanings assigned to them in accordance with generally
         accepted accounting principles, and, except as otherwise herein
         expressly provided, the term "generally accepted accounting principles"
         with respect to any computation required or permitted hereunder shall
         mean such accounting principles as are generally accepted at the date
         of such computation;

                           (4) unless the context otherwise requires, any
         reference to an "Article" or a "Section" refers to an Article or a
         Section, as the case may be, of this Indenture; and

                           (5) the words "herein," "hereof" and "hereunder" and
         other words of similar import refer to this Indenture as a whole and
         not to any particular Article, Section or other subdivision.

                  "Act," when used with respect to any Holder, has the meaning
specified in Section 1.4.

                  "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 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.

                  "Authenticating Agent" means any Person authorized by the
Trustee pursuant to Section 6.14 to act on behalf of the Trustee to authenticate
Securities of one or more series.

                  "Board of Directors" means either the board of directors of
the Company or any duly authorized committee of that board empowered to act for
it with respect to this Indenture.

                  "Board Resolution" means a copy of a resolution certified by
the Secretary or an Assistant Secretary of the Company to have been duly adopted
by the


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Board of Directors and to be in full force and effect on the date of such
certification, and delivered to the Trustee.

                  "Business Day," when used with respect to any Place of
Payment, means each Monday, Tuesday, Wednesday, Thursday and Friday which is not
a day on which banking institutions in that Place of Payment are authorized or
obligated by law or executive order to close.

                  "Commission" means the Securities and Exchange Commission,
from time to time constituted, created under the Exchange Act, or, if at any
time after the execution of this instrument such Commission is not existing and
performing the duties now assigned to it under the Trust Indenture Act, then the
body performing such duties at such time.

                  "Common Stock" includes any stock of any class of the Company,
which has no preference in respect of dividends or of amounts payable in the
event of any voluntary or involuntary liquidation, dissolution or winding-up of
the Company and which is not subject to redemption by the Company; provided,
however, subject to the provisions of Section 14.9, shares issuable upon
conversion of Securities shall include only shares of the class designated as
Common Stock of the Company at the date of this Indenture or shares of any class
or classes resulting from any reclassification or reclassifications thereof and
which have no preference in respect of dividends or of amounts payable in the
event of any voluntary or involuntary liquidation, dissolution or winding-up of
the Company and which are not subject to redemption by the Company; provided,
further that if at any time there shall be more than one such resulting class,
the shares of each such class then so issuable shall be substantially in the
proportion which the total number of shares of such class resulting from all
such reclassifications bears to the total number of shares of all such classes
resulting from all such reclassifications.

                  "Company" means the corporation named as the "Company" in the
first paragraph of this instrument until a successor Person shall have become
such pursuant to the applicable provisions of this Indenture, and thereafter
"Company" shall mean such successor Person.

                  "Company Request" or "Company Order" means a written request
or order signed in the name of the Company by its Chairman of the Board, its
President or a Vice President, and by its principal financial officer, its
Treasurer, an Assistant Treasurer, its Secretary or an Assistant Secretary, and
delivered to the Trustee.

                  "Constituent Person" has the meaning specified in Section
14.9.


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                  "Corporate Trust Office" means the corporate trust office of
the Trustee at [___________________________], Attention: Corporate Trust
Department, or such other office, designated by the Trustee by written notice to
the Company, at which at any particular time its corporate trust business shall
be administered.

                  "Corporation" means a corporation, association, company,
joint-stock company or business trust.

                  "Covenant Defeasance" has the meaning specified in Section
13.3.

                  "Credit Agreement" means that certain Credit Agreement, dated
as of [________________], among the Company, [________________],
[________________] and [________________] as amended through the date hereof, as
further amended, amended and restated, supplemented or otherwise modified from
time to time.

                  "Defaulted Interest" has the meaning specified in Section 3.7.

                  "Defeasance" has the meaning specified in Section 13.2.

                  "Depositary" means, with respect to Securities of any series
issuable in whole or in part in the form of one or more Global Securities, a
clearing agency registered under the Exchange Act that is designated to act as
Depositary for such Securities as contemplated by Section 3.1.

                  "Designated Senior Indebtedness" means the Credit Agreement
and any particular Senior Indebtedness in which the instrument creating or
evidencing the same or the assumption or guarantee thereof (or related
agreements or documents to which the Company is a party) expressly provides that
such Senior Indebtedness shall be "Designated Senior Indebtedness."

                  "Event of Default" has the meaning specified in Section 5.1.

                  "Exchange Act" means the Securities Exchange Act of 1934 and
any statute successor thereto, in each case as amended from time to time.

                  "Expiration Date" has the meaning specified in Section 1.4.

                  "Global Security" means a Security that evidences all or part
of the Securities of any series and bears the legend set forth in Section 2.2
(or such legend as may be specified as contemplated by Section 3.1 for such
Securities).


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                  "Holder" means a Person in whose name a Security is registered
in the Security Register.

                  "Indebtedness" means, with respect to any Person, and without
duplication, (a) all indebtedness, obligations and other liabilities (contingent
or otherwise) of such Person for borrowed money (including obligations of the
Company in respect of overdrafts, foreign exchange contracts, currency exchange
agreements, interest rate protection agreements, and any loans or advances from
banks, whether or not evidenced by notes or similar instruments) or evidenced by
bonds, debentures, notes or similar instruments (whether or not the recourse of
the lender is to the whole of the assets of such Person or to only a portion
thereof) (other than any account payable or other accrued current liability or
obligation incurred in the ordinary course of business in connection with the
obtaining of materials or services), (b) all reimbursement obligations and other
liabilities (contingent or otherwise) of such Person with respect to letters of
credit, bank guarantees or bankers' acceptances, (c) all obligations and
liabilities (contingent or otherwise) in respect of leases of such Person
required, in conformity with generally accepted accounting principles, to be
accounted for as capitalized lease obligations on the balance sheet of such
Person and all obligations and other liabilities (contingent or otherwise) under
any lease or related document (including a purchase agreement) in connection
with the lease of real property which provides that such Person is contractually
obligated to purchase or cause a third party to purchase the leased property and
thereby guarantee a minimum residual value of the leased property to the lessor
and the obligations of such Person under such lease or related document to
purchase or to cause a third party to purchase such leased property, (d) all
obligations of such Person (contingent or otherwise) with respect to an interest
rate or other swap, cap or collar agreement or other similar instrument or
agreement or foreign currency hedge, exchange, purchase or similar instrument or
agreement, (e) all direct or indirect guaranties or similar agreements by such
Person in respect of, and obligations or liabilities (contingent or otherwise)
of such Person to purchase or otherwise acquire or otherwise assure a creditor
against loss in respect of indebtedness, obligations or liabilities of another
Person of the kind described in clauses (a) through (d), (f) any indebtedness or
other obligations described in clauses (a) through (d) secured by any mortgage,
pledge, lien or other encumbrance existing on property which is owned or held by
such Person, regardless of whether the indebtedness or other obligation secured
thereby shall have been assumed by such Person and (g) any and all deferrals,
renewals, extensions and refundings of, or amendments, modifications or
supplements to, any indebtedness, obligation or liability of the kind described
in clauses (a) through (f).

                  "Indenture" means this instrument as originally executed and
as it may from time to time be supplemented or amended by one or more indentures


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<PAGE>   13


supplemental hereto entered into pursuant to the applicable provisions hereof,
including, for all purposes of this instrument and any such supplemental
indenture, the provisions of the Trust Indenture Act that are deemed to be a
part of and govern this instrument and any such supplemental indenture,
respectively. The term "Indenture" shall also include the terms of particular
series of Securities established as contemplated by Section 3.1; provided,
however, that if at any time more than one Person is acting as Trustee under
this Indenture due to the appointment of one or more separate Trustees for any
one or more separate series of Securities, "Indenture" shall mean, with respect
to such series of Securities for which any such Person is Trustee, this
instrument as originally executed or as it may from time to time be supplemented
or amended by one or more indentures supplemental hereto entered into pursuant
to the applicable provisions hereof and shall include the terms of particular
series of Securities for which such Person is Trustee established as
contemplated by Section 3.1, exclusive, however, of any provisions or terms
which relate solely to other series of Securities for which such Person is not
Trustee, regardless of when such terms or provisions were adopted, and exclusive
of any provisions or terms adopted by means of one or more indentures
supplemental hereto executed and delivered after such Person had become such
Trustee, but to which such person, as such Trustee, was not a party; provided,
further that in the event that this Indenture is supplemented or amended by one
or more indentures supplemental hereto which are only applicable to certain
series of Securities, the term "Indenture" for a particular series of Securities
shall only include the supplemental indentures applicable thereto.

                  "interest," when used with respect to an Original Issue
Discount Security which by its terms bears interest only after Maturity, means
interest payable after Maturity.

                  "Interest Payment Date," when used with respect to any
Security, means the Stated Maturity of an installment of interest on such
Security.

                  "Investment Company Act" means the Investment Company Act of
1940 and any statute successor thereto, in each case as amended from time to
time.

                  "Maturity," when used with respect to any Security, means the
date on which the principal of such Security or an installment of principal
becomes due and payable as therein or herein provided, whether at the Stated
Maturity or by declaration of acceleration, call for redemption or otherwise.

                  "Notice of Default" means a written notice of the kind
specified in Section 5.1(4).


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<PAGE>   14


                  "Officers' Certificate" means a certificate signed by the
Chairman of the Board, the President or a Vice President, and by the principal
financial officer, the Treasurer, an Assistant Treasurer, the Secretary or an
Assistant Secretary, of the Company, and delivered to the Trustee. One of the
officers signing an Officers' Certificate given pursuant to Section 10.4 shall
be the principal executive, financial or accounting officer of the Company.

                  "Opinion of Counsel" means a written opinion of counsel, who
may be counsel for, or an employee of, the Company, and who shall be reasonably
acceptable to the Trustee.

                  "Original Issue Discount Security" means any Security which
provides for an amount less than the principal amount thereof to be due and
payable upon a declaration of acceleration of the Maturity thereof pursuant to
Section 5.2.

                  "Outstanding," when used with respect to Securities, means, as
of the date of determination, all Securities theretofore authenticated and
delivered under this Indenture, except

                           (1) Securities theretofore canceled by the Trustee or
         delivered to the Trustee for cancellation;

                           (2) Securities for whose payment or redemption money
         in the necessary amount has been theretofore deposited with the Trustee
         or any Paying Agent (other than the Company) in trust or set aside and
         segregated in trust by the Company (if the Company shall act as its own
         Paying Agent) for the Holders of such Securities; provided that, if
         such Securities are to be redeemed, notice of such redemption has been
         duly given pursuant to this Indenture or provision therefor
         satisfactory to the Trustee has been made;

                           (3) Securities as to which Defeasance has been
         effected pursuant to Section 13.2; and

                           (4) Securities which have been paid pursuant to
         Section 3.6 or in exchange for or in lieu of which other Securities
         have been authenticated and delivered pursuant to this Indenture, other
         than any such Securities in respect of which there shall have been
         presented to the Trustee proof satisfactory to it that such Securities
         are held by a bona fide


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<PAGE>   15

         purchaser in whose hands such Securities are valid obligations of the
         Company;

provided, however, that in determining whether the Holders of the requisite
principal amount of the Outstanding Securities have given, made or taken any
request, demand, authorization, direction, notice, consent, waiver or other
action hereunder as of any date, (A) the principal amount of an Original Issue
Discount Security which shall be deemed to be Outstanding shall be the amount of
the principal thereof which would be due and payable as of such date upon
acceleration of the Maturity thereof to such date pursuant to Section 5.2, (B)
if, as of such date, the principal amount payable at the Stated Maturity of a
Security is not determinable, the principal amount of such Security which shall
be deemed to be Outstanding shall be the amount as specified or determined as
contemplated by Section 3.1, (C) the principal amount of a Security denominated
in one or more foreign currencies or currency units which shall be deemed to be
Outstanding shall be the U.S. dollar equivalent, determined as of such date in
the manner provided as contemplated by Section 3.1, of the principal amount of
such Security (or, in the case of a Security described in Clause (A) or (B)
above, of the amount determined as provided in such Clause), and (D) Securities
owned by the Company or any other obligor upon the Securities or any Affiliate
of the Company or of 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 action, only Securities which the Trustee knows
to be so owned shall be so disregarded. Securities so owned which have been
pledged in good faith may be regarded as Outstanding if the pledgee establishes
to the satisfaction of the Trustee the pledgee's right so to act with respect to
such Securities and that the pledgee is not the Company or any other obligor
upon the Securities or any Affiliate of the Company or of such other obligor.

                  "Paying Agent" means any Person authorized by the Company to
pay the principal of or any premium or interest on any Securities on behalf of
the Company.

                  "Payment Blockage Notice" has the meaning specified in Section
15.4.

                  "Person" means any individual, corporation, partnership, joint
venture, trust, unincorporated organization or government or any agency or
political subdivision thereof.

                  "Place of Payment," when used with respect to the Securities
of any series, means the place or places where the principal of and any premium
and interest


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<PAGE>   16

on the Securities of that series are payable as specified as contemplated by
Section 3.1.

                  "Predecessor Security" of any particular Security means every
previous Security evidencing all or a portion of the same debt as that evidenced
by such particular Security; and, for the purposes of this definition, any
Security authenticated and delivered under Section 3.6 in exchange for or in
lieu of a mutilated, destroyed, lost or stolen Security shall be deemed to
evidence the same debt as the mutilated, destroyed, lost or stolen Security.

                  "Record Date" means any Regular Record Date or Special Record
Date.

                  "Redemption Date," when used with respect to any Security to
be redeemed, means the date fixed for such redemption by or pursuant to this
Indenture.

                  "Redemption Price," when used with respect to any Security to
be redeemed, means the price at which it is to be redeemed pursuant to this
Indenture.

                  "Regular Record Date" for the interest payable on any Interest
Payment Date on the Securities of any series means the date specified for that
purpose as contemplated by Section 3.1.

                  "Representative" means (a) the indenture trustee or other
trustee, agent or representative for any Senior Indebtedness or (b) with respect
to any Senior Indebtedness that does not have any such trustee, agent or other
representative, (i) in the case of such Senior Indebtedness issued pursuant to
an agreement providing for voting arrangements as among the holders or owners of
such Senior Indebtedness, any holder or owner of such Senior Indebtedness acting
with the consent of the required persons necessary to bind such holders or
owners of such Senior Indebtedness and (ii) in the case of all other such Senior
Indebtedness, the holder or owner of such Senior Indebtedness.

                  "Responsible Officer" means any officer within the corporate
trust department of the Trustee, including any vice president, assistant vice
president, treasurer, assistant treasurer, trust officer, secretary or any
assistant secretary, or any other officer who customarily performs functions
similar to those performed by any of the above designated officers, and also,
regarding a particular matter, any other officer of the Trustee to whom the
matter is referred because of that officer's knowledge of and familiarity with
the particular subject.


                                       9
<PAGE>   17


                  "Securities" has the meaning stated in the first recital of
this Indenture and more particularly means any Securities authenticated and
delivered under this Indenture.

                  "Securities Act" means the Securities Act of 1933 and any
statute successor thereto, in each case as amended from time to time.

                  "Security Register" and "Security Registrar" have the
respective meanings specified in Section 3.5.

                  "Senior Indebtedness" means the principal of, premium, if any,
interest (including all interest accruing subsequent to the commencement of any
bankruptcy or similar proceeding, whether or not a claim for post-petition
interest is allowable as a claim in any such proceeding) and rent payable on or
in connection with, and all fees, costs, expenses and other amounts accrued or
due on or in connection with, Indebtedness of the Company, whether outstanding
on the date of this Indenture or thereafter created, incurred, assumed,
guaranteed or in effect guaranteed by the Company (including all deferrals,
renewals, extensions or refundings of, or amendments, modifications or
supplements to, the foregoing), unless in the case of any particular
Indebtedness the instrument creating or evidencing the same or the assumption or
guarantee thereof expressly provides that such Indebtedness shall not be senior
in right of payment to the Securities or expressly provides that such
Indebtedness is "pari passu" or "junior" to the Securities. Notwithstanding the
foregoing, the term Senior Indebtedness shall not include any Indebtedness of
the Company to any subsidiary of the Company, a majority of the voting stock of
which is owned, directly or indirectly, by the Company.

                  "Special Record Date" for the payment of any Defaulted
Interest means a date fixed by the Trustee pursuant to Section 3.7.

                  "Stated Maturity," when used with respect to any Security or
any installment of principal thereof or interest thereon, means the date
specified in such Security as the fixed date on which the principal of such
Security or such installment of principal or interest is due and payable.

                  "Subsidiary" means, with respect to any Person, (i) any
corporation or trust of which a majority of the outstanding voting securities is
at the time, and (ii) any partnership of which a majority of the equity capital
or profit interest is at the time, owned, directly or indirectly, by the
Company, by one or more other Subsidiaries or by the Company and one or more
Subsidiaries. For the purposes of this definition, "voting securities" means
securities which ordinarily have voting


                                       10
<PAGE>   18


power for the election of directors, whether at all times or only so long as no
senior class of securities has such voting power by reason of any contingency.

                  "Trust Indenture Act" means the Trust Indenture Act of 1939 as
in force at the date as of which this instrument was executed; provided,
however, that in the event the Trust Indenture Act of 1939 is amended after such
date, "Trust Indenture Act" means, to the extent required by any such amendment,
the Trust Indenture Act of 1939 as so amended.

                  "Trustee" means the Person named as the "Trustee" in the first
paragraph of this instrument until a successor Trustee shall have become such
pursuant to the applicable provisions of this Indenture, and thereafter
"Trustee" shall mean or include each Person who is then a Trustee hereunder, and
if at any time there is more than one such Person, "Trustee" as used with
respect to the Securities of any series shall mean the Trustee with respect to
Securities of that series.

                  "U.S. Government Obligation" has the meaning specified in
Section 13.4.

                  "Vice President," when used with respect to the Company or the
Trustee, means any vice president, whether or not designated by a number or a
word or words added before or after the title "vice president."

SECTION 1.2 COMPLIANCE CERTIFICATES AND OPINIONS.

                  Upon any application or request by the Company to the Trustee
to take any action under any provision of this Indenture, the Company shall
furnish to the Trustee such certificates and opinions as may be required under
the Trust Indenture Act. Each such certificate or opinion shall be given in the
form of an Officers' Certificate, if to be given by an officer of the Company,
or an Opinion of Counsel, if to be given by counsel, and shall comply with the
requirements of the Trust Indenture Act and any other requirements set forth in
this Indenture.

                  Every certificate or opinion with respect to compliance with a
condition or covenant provided for in this Indenture shall include,

                           (1) a statement that each individual signing such
         certificate or opinion has read such covenant or condition and the
         definitions herein relating thereto;


                                       11
<PAGE>   19


                           (2) a brief statement as to the nature and scope of
         the examination or investigation upon which the statements or opinions
         contained in such certificate or opinion are based;

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

                           (4) a statement as to whether, in the opinion of each
         such individual, such condition or covenant has been complied with.

SECTION 1.3 FORM OF DOCUMENTS DELIVERED TO TRUSTEE.

                  In any case where several matters are required to be certified
by, or covered by an opinion of, any specified Person, it is not necessary that
all such matters be certified by, or covered by the opinion of, only one such
Person, or that they be so certified or covered by only one document, but one
such Person may certify or give an opinion with respect to some matters and one
or more other such Persons as to other matters, and any such Person may certify
or give an opinion as to such matters in one or several documents.

                  Any certificate or opinion of an officer of the Company may be
based, insofar as it relates to legal matters, upon a certificate or opinion of,
or representations by, counsel, unless such officer knows, or in the exercise of
reasonable care should know, that the certificate or opinion or representations
with respect to the matters upon which his or her certificate or opinion is
based are erroneous. Any such certificate or opinion of counsel may be based,
insofar as it relates to factual matters, upon a certificate or opinion of, or
representations by, an officer or officers of the Company stating that the
information with respect to such factual matters is in the possession of the
Company, unless such counsel knows, or in the exercise of reasonable care should
know, that the certificate or opinion or representations with respect to such
matters are erroneous.

                  Where any Person is required to make, give or execute two or
more applications, requests, consents, certificates, statements, opinions or
other instruments under this Indenture, they may, but need not, be consolidated
and form one instrument.


                                       12
<PAGE>   20

SECTION 1.4 ACTS OF HOLDERS; RECORD DATES.

                  Any request, demand, authorization, direction, notice,
consent, waiver or other action provided or permitted by this Indenture to be
given, made or taken by Holders may be embodied in and evidenced by one or more
instruments of substantially similar tenor signed by such Holders in person or
by agent duly appointed in writing; and, except as herein otherwise expressly
provided, such action shall become effective when such instrument or instruments
are delivered to the Trustee and, where it is hereby expressly required, to the
Company. The Trustee shall promptly deliver to the Company copies of all such
instrument or instruments delivered to the Trustee. Such instrument or
instruments (and the action embodied therein and evidenced thereby) are herein
sometimes referred to as the "Act" of the Holders signing such instrument or
instruments. 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 (subject to Section 6.1) conclusive in favor of the Trustee and the Company,
if made in the manner provided in this Section.

                  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 him or her the execution thereof.
Where such execution is by a signer acting in a capacity other than his or her
individual capacity, such certificate or affidavit shall also constitute
sufficient proof of his or her authority. 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.

                  The ownership of Securities shall be proved by the Security
Register.

                  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.

                  The Company may set any day as a record date for the purpose
of determining the Holders of Outstanding Securities of any series entitled to
give, make or take any request, demand, authorization, direction, vote, notice,
consent, waiver or other action provided or permitted by this Indenture to be
given, made or taken by Holders of Securities of such series, provided that the
Company may not set a record date for, and the provisions of this paragraph
shall not apply with respect to,


                                       13
<PAGE>   21


the giving or making of any notice, declaration, request or direction referred
to in the next paragraph. If any record date is set pursuant to this paragraph,
the Holders of Outstanding Securities of the relevant series on such record
date, and no other Holders, shall be entitled to take the relevant action,
whether or not such Holders remain Holders after such record date; provided that
no such action shall be effective hereunder unless taken on or prior to the
applicable Expiration Date by Holders of the requisite principal amount of
Outstanding Securities of such series on such record date. Nothing in this
paragraph shall be construed to prevent the Company from setting a new record
date for any action for which a record date has previously been set pursuant to
this paragraph (whereupon the record date previously set shall automatically and
with no action by any Person be canceled and of no effect), and nothing in this
paragraph shall be construed to render ineffective any action taken by Holders
of the requisite principal amount of Outstanding Securities of the relevant
series on the date such action is taken. Promptly after any record date is set
pursuant to this paragraph, the Company, at its own expense, shall cause notice
of such record date, the proposed action by Holders and the applicable
Expiration Date to be given to the Trustee in writing and to each Holder of
Securities of the relevant series in the manner set forth in Section 1.6.

                  The Trustee may set any day as a record date for the purpose
of determining the Holders of Outstanding Securities of any series entitled to
join in the giving or making of (i) any Notice of Default, (ii) any declaration
of acceleration referred to in Section 5.2, (iii) any request to institute
proceedings referred to in Section 5.7(2) or (iv) any direction referred to in
Section 5.12, in each case with respect to Securities of such series. If any
record date is set pursuant to this paragraph, the Holders of Outstanding
Securities of such series on such record date, and no other Holders, shall be
entitled to join in such notice, declaration, request or direction, whether or
not such Holders remain Holders after such record date; provided that no such
action shall be effective hereunder unless taken on or prior to the applicable
Expiration Date by Holders of the requisite principal amount of Outstanding
Securities of such series on such record date. Nothing in this paragraph shall
be construed to prevent the Trustee from setting a new record date for any
action for which a record date has previously been set pursuant to this
paragraph (whereupon the record date previously set shall automatically and with
no action by any Person be canceled and of no effect), and nothing in this
paragraph shall be construed to render ineffective any action taken by Holders
of the requisite principal amount of Outstanding Securities of the relevant
series on the date such action is taken. Promptly after any record date is set
pursuant to this paragraph, the Trustee, at the Company's expense, shall cause
notice of such record date, the proposed action by Holders and the applicable
Expiration Date to be given to the Company in writing and to each Holder of
Securities of the relevant series in the manner set forth in Section 1.6.


                                       14
<PAGE>   22


                  With respect to any record date set pursuant to this Section,
the party hereto which sets such record dates may designate any day as the
"Expiration Date" and from time to time may change the Expiration Date to any
earlier or later day; provided that no such change shall be effective unless
notice of the proposed new Expiration Date is given to the other party hereto in
writing, and to each Holder of Securities of the relevant series in the manner
set forth in Section 1.6, on or prior to the existing Expiration Date. If an
Expiration Date is not designated with respect to any record date set pursuant
to this Section, the party hereto which set such record date shall be deemed to
have initially designated the 180th day after such record date as the Expiration
Date with respect thereto, subject to its right to change the Expiration Date as
provided in this paragraph. Notwithstanding the foregoing, no Expiration Date
shall be later than the 180th day after the applicable record date.

                  Without limiting the foregoing, a Holder entitled hereunder to
take any action hereunder with regard to any particular Security may do so with
regard to all or any part of the principal amount of such Security or by one or
more duly appointed agents each of which may do so pursuant to such appointment
with regard to all or any part of such principal amount.

SECTION 1.5 NOTICES, ETC., TO TRUSTEE AND COMPANY.

                  Any request, demand, authorization, direction, notice,
consent, waiver or Act of Holders or other document provided or permitted by
this Indenture to be made upon, given or furnished to, or filed with,

                           (1) the Trustee by any Holder or by the Company shall
         be sufficient for every purpose hereunder if made, given, furnished or
         filed in writing (or by facsimile transmissions, provided that oral
         confirmation of receipt shall have been received) to or with the
         Trustee at its Corporate Trust Office, Attention: Corporate Trust
         Department, or

                           (2) the Company by the Trustee or by any Holder shall
         be sufficient for every purpose hereunder (unless otherwise herein
         expressly provided) if in writing and mailed, first-class postage
         prepaid, to the Company addressed to it at the address of its principal
         office specified in the first paragraph of this instrument or at any
         other address previously furnished in writing to the Trustee by the
         Company, Attention: Chief Financial Officer.


                                       15
<PAGE>   23

SECTION 1.6 NOTICE TO HOLDERS; WAIVER.

                  Where this Indenture provides for notice to Holders of any
event, such notice shall be sufficiently given (unless otherwise herein
expressly provided) if in writing and mailed, first-class postage prepaid, or
delivered by hand or overnight courier to each Holder affected by such event, at
its address as it appears in the Security Register, not later than the latest
date (if any), and not earlier than the earliest date (if any), prescribed for
the giving of such notice. Neither the failure to mail or deliver by hand or
overnight courier any such notice, nor any defect in any such notice so mailed
or delivered by hand or overnight courier, to any particular Holder shall affect
the sufficiency of such notice with respect to other Holders. Where this
Indenture provides for notice in any manner, such notice may be waived in
writing by the Person entitled to receive such notice, either before or after
the event, and such waiver shall be the equivalent of such notice. Waivers of
notice by Holders shall be filed with the Trustee, but such filing shall not be
a condition precedent to the validity of any action taken in reliance upon such
waiver.

                  In case by reason of the suspension of regular mail service or
by reason of any other cause it shall be impracticable to give such notice by
mail, then such notification as shall be made with the approval of the Trustee
shall constitute a sufficient notification for every purpose hereunder.

SECTION 1.7 CONFLICT WITH TRUST INDENTURE ACT.

                  If any provision hereof limits, qualifies or conflicts with a
provision of the Trust Indenture Act which is required under such Act to be a
part of and govern this Indenture, the latter provision shall control. If any
provision of this Indenture modifies or excludes any provision of the Trust
Indenture Act which may be so modified or excluded, the latter provision shall
be deemed to apply to this Indenture as so modified or to be excluded, as the
case may be.

SECTION 1.8 EFFECT OF HEADINGS AND TABLE OF CONTENTS.

                  The Article and Section headings herein and the Table of
Contents are for convenience only and shall not affect the construction hereof.

SECTION 1.9 SUCCESSORS AND ASSIGNS.

                  All covenants and agreements in this Indenture by the Company
shall bind its successors and assigns, whether so expressed or not.


                                       16
<PAGE>   24


SECTION 1.10 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 1.11 BENEFITS OF INDENTURE.

                  Nothing in this Indenture or in the Securities, express or
implied, shall give to any Person, other than the parties hereto and their
successors hereunder, the holders of Senior Indebtedness and the Holders, any
benefit or any legal or equitable right, remedy or claim under this Indenture.

SECTION 1.12 GOVERNING LAW.

                  THIS INDENTURE AND THE SECURITIES SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAW OF THE STATE OF NEW YORK, WITHOUT GIVING
EFFECT TO SUCH STATE'S CONFLICTS OF LAWS PRINCIPLES.

SECTION 1.13 LEGAL HOLIDAYS.

                  In any case where any Interest Payment Date, Redemption Date
or Stated Maturity of any Security or the last date on which a Holder has the
right to convert a Security at a particular conversion price shall not be a
Business Day at any Place of Payment, then (notwithstanding any other provision
of this Indenture or of the Securities (other than a provision of any Security
which specifically states that such provision shall apply in lieu of this
Section)) payment of interest or principal (and premium, if any) or, if
applicable to a particular series of Securities, conversion need not be made at
such Place of Payment on such date, but may be made on the next succeeding
Business Day at such Place of Payment with the same force and effect as if made
on the Interest Payment Date or Redemption Date, at the Stated Maturity or on
such last day for conversion, as the case may be.

SECTION 1.14 INDENTURE AND SECURITIES SOLELY CORPORATE OBLIGATIONS.

                  No recourse for the payment of the principal of or premium, if
any, or interest on any Security, or for any claim based thereon or otherwise in
respect thereof, and no recourse under or upon any obligation, covenant or
agreement of the Company in this Indenture or in any supplemental indenture or
in any Security, or because of the creation of any indebtedness represented
thereby, shall be had against any incorporator, stockholder, employee, agent,
officer, or director or subsidiary, as such, past, present or future, of the
Company or of any successor corporation, either


                                       17
<PAGE>   25


directly or through the Company or any successor corporation, whether by virtue
of any constitution, statute or rule of law, or by the enforcement of any
assessment or penalty or otherwise; it being expressly understood that all such
liability is hereby expressly waived and released as a condition of, and as a
consideration for, the execution of this Indenture and the issue of the
Securities.

SECTION 1.15 INDENTURE MAY BE EXECUTED IN COUNTERPARTS.

                  This instrument may be executed in any number of counterparts,
each of which shall be an original, but such counterparts shall together
constitute but one and the same instruments.


                                   ARTICLE II

                                 SECURITY FORMS

SECTION 2.1 FORMS GENERALLY.

                  The Securities of each series shall be in substantially the
form set forth in this Article, or in such other form as shall be established by
or pursuant to a Board Resolution or in one or more indentures supplemental
hereto, in each case with such appropriate insertions, omissions, substitutions
and other variations as are required or permitted by this Indenture, and may
have such letters, numbers or other marks of identification and such legends or
endorsements placed thereon as may be required to comply with the rules of any
securities exchange or Depositary therefor or as may, consistently herewith, be
determined by the officers executing such Securities, as evidenced by their
execution thereof. If the form of Securities of any series is established by
action taken pursuant to a Board Resolution, a copy of an appropriate record of
such action shall be certified by the Secretary or an Assistant Secretary of the
Company and delivered to the Trustee at or prior to the delivery of the Company
Order contemplated by Section 3.3 for the authentication and delivery of such
Securities. Any such Board Resolution or record of such action shall have
attached thereto a true and correct copy of the form of Security referred to
therein approved by or pursuant to such Board Resolution.

SECTION 2.2 FORM OF LEGEND FOR GLOBAL SECURITIES.

                  Unless otherwise specified as contemplated by Section 3.1 for
the Securities evidenced thereby, every Global Security authenticated and
delivered hereunder shall bear a legend in substantially the following form:


                                       18
<PAGE>   26


                  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 MAY NOT BE EXCHANGED IN WHOLE OR IN PART FOR
A SECURITY REGISTERED, AND NO TRANSFER OF THIS SECURITY IN WHOLE OR IN PART MAY
BE REGISTERED, IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR A NOMINEE
THEREOF, EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE INDENTURE.

SECTION 2.3 FORM OF TRUSTEE'S CERTIFICATE OF AUTHENTICATION.

                  The Trustee's certificates of authentication shall be in
substantially the following form:

                  This is one of the Securities of the series designated herein
referred to in the within-mentioned Indenture.

                                    [                     ],
                                     ---------------------
                                      as Trustee


                                    By:
                                       ---------------------
                                         Authorized Officer

SECTION 2.4 FORM OF CONVERSION NOTICE.

                  Conversion notices shall be in substantially the following
form:

To Willbros Group, Inc.:

                  The undersigned owner of this Security hereby irrevocably
exercises the option to convert this Security, or portion hereof (which is
$1,000 or an integral multiple thereof) below designated, into shares of Common
Stock of the Company in accordance with the terms of the Indenture referred to
in this Security, and directs that the shares issuable and deliverable upon the
conversion, together with any check in payment for fractional shares and any
Securities representing any unconverted principal amount hereof, be issued and
delivered to the registered holder hereof unless a different name has been
indicated below. If this Notice is being delivered on a date after the close of
business on a Regular Record Date and prior to the opening of business on the
related Interest Payment Date (unless this Security or the portion


                                       19
<PAGE>   27


thereof being converted has been called for redemption on a Redemption Date
during the period beginning at the close of business on a Regular Record Date
and ending at the opening of business on the first Business Day after the next
succeeding Interest Payment Date, or if such Interest Payment Date is not a
Business Day, the second such Business Day), this Notice is accompanied by
payment, in funds acceptable to the Company, of an amount equal to the interest
payable on such Interest Payment Date of the principal of this Security to be
converted. If shares are to be issued in the name of a person other than the
undersigned, the undersigned will pay all transfer taxes payable with respect
hereto. Any amount required to be paid by the undersigned on account of interest
accompanies this Security.

              Principal Amount to be Converted
         (in an integral multiple of $1,000, if less than all)

U.S. $
      ---------
Dated:
      -------------
                           Signature(s) must be guaranteed by an eligible
                           guarantor institution (banks, stock brokers, savings
                           and loan associations and credit unions with
                           membership in an approved signature guarantee
                           medallion program) pursuant to Securities and
                           Exchange Commission Rule 17Ad-15.

                                     -----------------------------------
                                     Signature Guaranty

         Fill in for registration of shares of Common Stock and Security if to
be issued otherwise than to the registered Holder.


-------------------------           -------------------------------------
(Name)                              Social Security or Other Taxpayer
                                    Identification Number

-------------------------
(Address)


-----------------------------
Please print Name and Address
(including zip code number)


                                       20
<PAGE>   28


[The above conversion notice is to be modified, as appropriate, for conversion
into other securities or property of the Company.]


                                   ARTICLE III

                                 THE SECURITIES

SECTION 3.1 AMOUNT UNLIMITED; ISSUABLE IN SERIES.

                  The aggregate principal amount of Securities which may be
authenticated and delivered under this Indenture is unlimited.

                  The Securities may be issued in one or more series. There
shall be established in or pursuant to a Board Resolution and, subject to
Section 3.3, set forth, or determined in the manner provided, in an Officers'
Certificate, or established in one or more indentures supplemental hereto, prior
to the issuance of Securities of any series,

                           (1) the title of the Securities of the series (which
         shall distinguish the Securities of the series from Securities of any
         other series);

                           (2) any limit upon the aggregate principal amount of
         the Securities of the series which may be authenticated and delivered
         under this Indenture (except for Securities authenticated and delivered
         upon registration of transfer of, or in exchange for, or in lieu of,
         other Securities of the series pursuant to Section 3.4, 3.5, 3.6, 9.6
         or 11.7 and except for any Securities which, pursuant to Section 3.3,
         are deemed never to have been authenticated and delivered hereunder);

                           (3) the Person to whom any interest on a Security of
         the series shall be payable, if other than the Person in whose name
         that Security (or one or more Predecessor Securities) is registered at
         the close of business on the Regular Record Date for such interest;

                           (4) the date or dates on which the principal of any
         Securities of the series is payable;

                           (5) the rate or rates at which any Securities of the
         series shall bear interest, if any, the date or dates from which any
         such

                                       21
<PAGE>   29


         interest shall accrue, the Interest Payment Dates on which any such
         interest shall be payable and the Regular Record Date for any such
         interest payable on any Interest Payment Date;

                           (6) the place or places where the principal of and
         any premium and interest on any Securities of the series shall be
         payable;

                           (7) the period or periods within which, the price or
         prices at which and the terms and conditions upon which any Securities
         of the series may be redeemed, in whole or in part, at the option of
         the Company and, if other than by a Board Resolution, the manner in
         which any election by the Company to redeem the Securities shall be
         evidenced;

                           (8) the obligation, if any, of the Company to redeem
         or purchase any Securities of the series pursuant to any sinking fund
         or analogous provisions or at the option of the Holder thereof and the
         period or periods within which, the price or prices at which and the
         terms and conditions upon which any Securities of the series shall be
         redeemed or purchased, in whole or in part, pursuant to such
         obligation;

                           (9) if other than denominations of $1,000 and any
         integral multiple thereof, the denominations in which any Securities of
         the series shall be issuable;

                           (10) if the amount of principal of or any premium or
         interest on any Securities of the series may be determined with
         reference to an index or pursuant to a formula, the manner in which
         such amounts shall be determined;

                           (11) if other than the currency of the United States
         of America, the currency, currencies or currency units in which the
         principal of or any premium or interest on any Securities of the series
         shall be payable and the manner of determining the equivalent thereof
         in the currency of the United States of America for any purpose,
         including for purposes of the definition of "Outstanding" in Section
         1.1;

                           (12) if the principal of or any premium or interest
         on any Securities of the series is to be payable, at the election of
         the


                                       22
<PAGE>   30


         Company or the Holder thereof, in one or more currencies or currency
         units other than that or those in which such Securities are stated to
         be payable, the currency, currencies or currency units in which the
         principal of or any premium or interest on such Securities as to which
         such election is made shall be payable, the periods within which and
         the terms and conditions upon which such election is to be made and the
         amount so payable (or the manner in which such amount shall be
         determined);

                           (13) if other than the entire principal amount
         thereof, the portion of the principal amount of any Securities of the
         series which shall be payable upon declaration of acceleration of the
         Maturity thereof pursuant to Section 5.2;

                           (14) if the principal amount payable at the Stated
         Maturity of any Securities of the series will not be determinable as of
         any one or more dates prior to the Stated Maturity, the amount which
         shall be deemed to be the principal amount of such Securities as of any
         such date for any purpose thereunder or hereunder, including the
         principal amount thereof which shall be due and payable upon any
         Maturity other than the Stated Maturity or which shall be deemed to be
         Outstanding as of any date prior to the Stated Maturity (or, in any
         such case, the manner in which such amount deemed to be the principal
         amount shall be determined);

                           (15) if applicable, that the Securities of the
         series, in whole or any specified part, shall be defeasible pursuant to
         Section 13.2 or Section 13.3 or both such Sections and, if other than
         by a Board Resolution, the manner in which any election by the Company
         to defease such Securities shall be evidenced;

                           (16) if applicable, the terms of any right to convert
         Securities of the series into shares of Common Stock of the Company or
         other securities or property;

                           (17) if applicable, that any Securities of the series
         shall be issuable in whole or in part in the form of one or more Global
         Securities and, in such case, the respective Depositaries for such
         Global Securities, the form of any legend or legends which shall be
         borne by any such Global Security in addition to or in lieu of that set
         forth in Section 2.2 and any circumstances in addition to or in lieu of
         those set forth in Clause (2) of the last paragraph of Section 3.5 in


                                       23
<PAGE>   31


         which any such Global Security may be exchanged in whole or in part for
         Securities registered, and any transfer of such Global Security in
         whole or in part may be registered, in the name or names of Persons
         other than the Depositary for such Global Security or a nominee
         thereof;

                           (18) whether all of the provisions of this Indenture
         relating to the subordination of the Securities (including the
         provisions of Article 15), or different subordination provisions,
         including a different definition of "Senior Indebtedness" or
         "Designated Senior Indebtedness," will apply to Securities of the
         series;

                           (19) any addition to or change in the Events of
         Default which applies to any Securities of the series and any change in
         the right of the Trustee or the requisite Holders of such Securities to
         declare the principal amount thereof due and payable pursuant to
         Section 5.2;

                           (20) any addition to or change in the covenants set
         forth in Article 10 which applies to Securities of the series; and

                           (21) any other terms of the series (which terms shall
         not be inconsistent with the provisions of this Indenture, except as
         permitted by Section 9.1(5)).

                  All Securities of any one series shall be substantially
identical except as to denomination and except as may otherwise be provided in
or pursuant to the Board Resolution referred to above and (subject to Section
3.3) set forth, or determined in the manner provided, in the Officers'
Certificate referred to above or in any such indenture supplemental hereto.

                  If any of the terms of the series are established by action
taken pursuant to a Board Resolution, a copy of an appropriate record of such
action shall be certified by the Secretary or an Assistant Secretary of the
Company and delivered to the Trustee at or prior to the delivery of the
Officers' Certificate setting forth the terms of the series.

                  The Securities shall be subordinated in right of payment to
Senior Indebtedness as provided in Article 15.


                                       24
<PAGE>   32


SECTION 3.2 DENOMINATIONS.

                  The Securities of each series shall be issuable only in
registered form without coupons and only in such denominations as shall be
specified as contemplated by Section 3.1. In the absence of any such specified
denomination with respect to the Securities of any series, the Securities of
such series shall be issuable in denominations of $1,000 and any integral
multiple thereof.

SECTION 3.3 EXECUTION, AUTHENTICATION, DELIVERY AND DATING.

                  The Securities shall be executed on behalf of the Company by
its Chairman of the Board, its Chief Executive Officer, its principal financial
officer, its President or one of its Vice Presidents, attested by its Treasurer,
Secretary or one of its Assistant Treasurers or Assistant Secretaries. The
signature of any of these officers on the Securities may be manual or facsimile.

                  Securities bearing the manual or facsimile signatures of
individuals who were at any time the proper officers of the Company shall bind
the Company, notwithstanding that such individuals or any of them have ceased to
hold such offices prior to the authentication and delivery of such Securities or
did not hold such offices at the date of such Securities.

                  At any time and from time to time after the execution and
delivery of this Indenture, the Company may deliver Securities of any series
executed by the Company to the Trustee for authentication, together with a
Company Order for the authentication and delivery of such Securities, and the
Trustee in accordance with the Company Order shall authenticate and deliver such
Securities. If the form or terms of the Securities of the series have been
established by or pursuant to one or more Board Resolutions as permitted by
Sections 2.1 and 3.1, in authenticating such Securities, and accepting the
additional responsibilities under this Indenture in relation to such Securities,
the Trustee shall be entitled to receive, and (subject to Section 6.1) shall be
fully protected in relying upon, a copy of such Board Resolution, the Officers'
Certificate setting forth the terms of the series and an Opinion of Counsel,
with such Opinion of Counsel stating,

                           (1) if the form of such Securities has been
         established by or pursuant to Board Resolution as permitted by Section
         2.1, that such form has been established in conformity with the
         provisions of this Indenture;

                           (2) if the terms of such Securities have been
         established by or pursuant to Board Resolution as permitted by


                                       25
<PAGE>   33

         Section 3.1, that such terms have been established in conformity with
         the provisions of this Indenture; and

                          (3) that such Securities, when authenticated and
         delivered by the Trustee and issued by the Company in the manner and
         subject to any conditions specified in such Opinion of Counsel, will
         constitute valid and legally binding obligations of the Company
         enforceable in accordance with their terms, subject to bankruptcy,
         insolvency, fraudulent transfer, reorganization, moratorium and similar
         laws of general applicability relating to or affecting creditors'
         rights and to general equity principles.

                  If such form or terms have been so established, the Trustee
shall not be required to authenticate such Securities if the issue of such
Securities pursuant to this Indenture will affect the Trustee's own rights,
duties or immunities under the Securities and this Indenture or otherwise in a
manner which is not reasonably acceptable to the Trustee.

                  Notwithstanding the provisions of Section 3.1 and of the
preceding paragraph, if all Securities of a series are not to be originally
issued at one time, it shall not be necessary to deliver the Officers'
Certificate otherwise required pursuant to Section 3.1 or the Company Order and
Opinion of Counsel otherwise required pursuant to such preceding paragraph at or
prior to the authentication of each Security of such series if such documents
are delivered at or prior to the authentication upon original issuance of the
first Security of such series to be issued.

                  Each Security shall be dated the date of its authentication.

                  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 executed by the Trustee by manual signature, and such certificate upon
any Security shall be conclusive evidence, and the only evidence, that such
Security has been duly authenticated and delivered hereunder. Notwithstanding
the foregoing, if any Security shall have been authenticated and delivered
hereunder but never issued and sold by the Company, and the Company shall
deliver such Security to the Trustee for cancellation as provided in Section
3.9, for all purposes of this Indenture such Security shall be deemed never to
have been authenticated and delivered hereunder and shall never be entitled to
the benefits of this Indenture.

                  Neither the Company nor the Trustee shall have any
responsibility for any defect in the CUSIP number that appears on any Security,
check, advice of

                                       26
<PAGE>   34


payment or redemption notice, and any such document may contain a statement to
the effect that CUSIP numbers have been assigned by an independent service for
convenience of reference and that neither the Company nor the Trustee shall be
liable for any inaccuracy in such numbers.

SECTION 3.4 TEMPORARY SECURITIES.

                  Pending the preparation of definitive Securities of any
series, 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
evidenced by their execution of such Securities.

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

SECTION 3.5 REGISTRATION; REGISTRATION OF TRANSFER AND EXCHANGE.

                  The Company shall cause to be kept at the Corporate Trust
Office of the Trustee a register (the register maintained in such office and in
any other office or agency of the Company in a Place of Payment being herein
sometimes collectively referred to as the "Security Register") in which, subject
to such reasonable regulations as it may prescribe, the Company shall provide
for the registration of Securities and of transfers of Securities. The Trustee
is hereby appointed "Security Registrar" for the purpose of registering
Securities and transfers of Securities as herein provided.


                                       27
<PAGE>   35


                  Upon surrender for registration of transfer of any Security of
a series at the office or agency of the Company in a Place of Payment for that
series, the Company shall execute, and the Trustee shall authenticate and
deliver, in the name of the designated transferee or transferees, one or more
new Securities of the same series, of any authorized denominations and of like
tenor and aggregate principal amount.

                  At the option of the Holder, Securities of any series may be
exchanged for other Securities of the same series, of any authorized
denominations and of like tenor and aggregate principal amount, upon surrender
of the Securities to be exchanged at such office or agency. Whenever any
Securities are so surrendered for exchange, the Company shall execute, and the
Trustee shall authenticate and deliver, the Securities which the Holder making
the exchange is entitled to receive.

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

                  Every Security presented or surrendered for registration of
transfer or for exchange shall (if so required by the Company or the Trustee) be
duly endorsed, or be accompanied by a written instrument of transfer in form
satisfactory to the Company and the Security Registrar duly executed, by the
Holder thereof or its attorney duly authorized in writing.

                  No service charge shall be made for any registration of
transfer or exchange of Securities, but the Company may require payment of a sum
sufficient to cover any tax or other governmental charge that may be imposed in
connection with any registration of transfer or exchange of Securities, other
than exchanges pursuant to Section 3.4, 9.6 or 11.7 not involving any transfer.

                  If the Securities of any series (or of any series and
specified tenor) are to be redeemed in part, the Company shall not be required
(A) to issue, register the transfer of or exchange any Securities of that series
(or of that series and specified tenor, as the case may be) during a period
beginning at the opening of business 15 days before the day of the mailing of a
notice of redemption of any such Securities selected for redemption under
Section 11.3 and ending at the close of business on the day of such mailing, or
(B) to register the transfer of or exchange any Security so selected for
redemption in whole or in part, except the unredeemed portion of any Security
being redeemed in part.


                                       28
<PAGE>   36


                  The provisions of Clauses (1), (2), (3) and (4) below shall
apply only to Global Securities:

                           (1) Each Global Security authenticated under this
         Indenture shall be registered in the name of the Depositary designated
         for such Global Security or a nominee thereof and delivered to such
         Depositary or a nominee thereof or custodian therefor, and each such
         Global Security shall constitute a single Security for all purposes of
         this Indenture.

                           (2) Notwithstanding any other provision in this
         Indenture, no Global Security may be exchanged in whole or in part for
         Securities registered, and no transfer of a Global Security in whole or
         in part may be registered, in the name of any Person other than the
         Depositary for such Global Security or a nominee thereof unless (A)
         such Depositary (i) has notified the Company that it is unwilling or
         unable to continue as Depositary for such Global Security or (ii) has
         ceased to be a clearing agency registered under the Exchange Act, (B)
         there shall have occurred and be continuing an Event of Default with
         respect to such Global Security or (C) there shall exist such
         circumstances, if any, in addition to or in lieu of the foregoing as
         have been specified for this purpose as contemplated by Section 3.1.

                           (3) Subject to Clause (2) above, any exchange of a
         Global Security for other Securities may be made in whole or in part,
         and all Securities issued in exchange for a Global Security or any
         portion thereof shall be registered in such names as the Depositary for
         such Global Security shall direct.

                           (4) Every Security authenticated and delivered upon
         registration of transfer of, or in exchange for or in lieu of, a Global
         Security or any portion thereof, whether pursuant to this Section,
         Section 3.4, 3.6, 9.6 or 11.7 or otherwise, shall be authenticated and
         delivered in the form of, and shall be, a Global Security, unless such
         Security is registered in the name of a Person other than the
         Depositary for such Global Security or a nominee thereof.

SECTION 3.6 MUTILATED, DESTROYED, LOST AND STOLEN SECURITIES.

                  If any mutilated Security is surrendered to the Trustee, the
Company shall execute and the Trustee shall authenticate and deliver in exchange
therefor a

                                       29
<PAGE>   37


new Security of the same series and of like tenor and principal amount and
bearing a number not contemporaneously outstanding.

                  If there shall be delivered to the Company and the Trustee (i)
evidence to their satisfaction of the destruction, loss or theft of any Security
and (ii) such security or indemnity as may be required by them to save each of
them and any agent of either of them harmless, then, in the absence of notice to
the Company or the Trustee that such Security has been acquired by a bona fide
purchaser, the Company shall execute and the Trustee shall authenticate and
deliver, in lieu of any such destroyed, lost or stolen Security, a new Security
of the same series and of like tenor and principal amount and bearing a number
not contemporaneously outstanding.

                  In case any such mutilated, destroyed, lost or stolen Security
has become or is about to become due and payable, the Company in its discretion
may, instead of issuing a new Security, pay such Security.

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

                  Every new Security of any series issued pursuant to this
Section in lieu of any 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 the benefits of this Indenture equally and
proportionately with any and all other Securities of that series duly issued
hereunder.

                  The provisions of this Section 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 3.7 PAYMENT OF INTEREST; INTEREST RIGHTS PRESERVED.

                  Except as otherwise provided as contemplated by Section 3.1
with respect to any series of Securities, interest on any Security which is
payable, and is punctually paid or duly provided for, on any Interest Payment
Date shall be paid to the Person in whose name that Security (or one or more
Predecessor Securities) is registered at the close of business on the Regular
Record Date for such interest.

                  Any interest on any Security of any series which is payable,
but is not punctually paid or duly provided for, on any Interest Payment Date
(herein called


                                       30
<PAGE>   38


"Defaulted Interest") shall forthwith cease to be payable to the Holder on the
relevant Regular Record Date by virtue of having been such Holder, and such
Defaulted Interest may be paid by the Company, at its election in each case, as
provided in Clause (1) or (2) below:

                           (1) The Company may elect to make payment of any
         Defaulted Interest to the Persons in whose names the Securities of such
         series (or their respective Predecessor Securities) are registered at
         the close of business on a Special Record Date for the payment of such
         Defaulted Interest, which shall be fixed in the following manner. The
         Company shall notify the Trustee in writing of the amount of Defaulted
         Interest proposed to be paid on each Security of such series and the
         date of the proposed payment, and at the same time the Company shall
         deposit with the Trustee an amount of money equal to the aggregate
         amount proposed to be paid in respect of such Defaulted Interest or
         shall make arrangements satisfactory to the Trustee for such deposit
         prior to the date of the proposed payment, such money when deposited to
         be held in trust for the benefit of the Persons entitled to such
         Defaulted Interest as in this Clause provided. Thereupon the Trustee
         shall fix a Special Record Date for the payment of such Defaulted
         Interest which shall be not more than 15 days and not less than 10 days
         prior to the date of the proposed payment and not less than 10 days
         after the receipt by the Trustee of the notice of the proposed payment.
         The Trustee shall promptly notify the Company of such Special Record
         Date and, in the name and at the expense of the Company, shall cause
         notice of the proposed payment of such Defaulted Interest and the
         Special Record Date therefor to be given to each Holder of Securities
         of such series in the manner set forth in Section 1.6, not less than 10
         days prior to such Special Record Date. Notice of the proposed payment
         of such Defaulted Interest and the Special Record Date therefor having
         been so mailed, such Defaulted Interest shall be paid to the Persons in
         whose names the Securities of such series (or their respective
         Predecessor Securities) are registered at the close of business on such
         Special Record Date and shall no longer be payable pursuant to the
         following Clause (2).

                           (2) The Company may make payment of any Defaulted
         Interest on the Securities of any series in any other lawful manner not
         inconsistent with the requirements of any securities exchange on which
         such Securities may be listed, and upon such notice as may be required
         by such exchange, if, after notice given by the Company to the Trustee
         of the proposed payment pursuant to this


                                       31
<PAGE>   39


         Clause, such manner of payment as shall be deemed practicable by the
         Trustee.

                  Subject to the foregoing provisions of this Section, each
Security delivered under this Indenture upon registration of transfer of or in
exchange for or in lieu of any other Security shall carry the rights to interest
accrued and unpaid, and to accrue, which were carried by such other Security.

                  Subject to the provisions of Section 14.2, in the case of any
Security (or any part thereof) which is converted after any Regular Record Date
and on or prior to the next succeeding Interest Payment Date (other than any
Security the principal of (or premium, if any, on) which shall become due and
payable, whether at Stated Maturity or by declaration of acceleration prior to
such Interest Payment Date), interest whose Stated Maturity is on such Interest
Payment Date shall be payable on such Interest Payment Date notwithstanding such
conversion and such interest (whether or not punctually paid or duly provided
for) shall be paid to the Person in whose name that Security (or any one or more
Predecessor Securities) is registered at the close of business on such Regular
Record Date. Except as otherwise expressly provided in the immediately preceding
sentence or in Section 14.2, in the case of any Security (or any part thereof)
which is converted, interest whose Stated Maturity is after the date of
conversion of such Security (or such part thereof) shall not be payable.

SECTION 3.8 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 and any
premium and (subject to Section 3.7) any interest on such Security 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 3.9   CANCELLATION.

                  All Securities surrendered for payment, redemption,
registration of transfer or exchange or for credit against any sinking fund
payment shall, if surrendered to any Person other than the Trustee, be delivered
to the Trustee and shall be promptly canceled 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 may deliver to the Trustee (or to any other Person for delivery
to the Trustee) for cancellation any


                                       32
<PAGE>   40


Securities previously authenticated hereunder which the Company has not issued
and sold, and all Securities so delivered shall be promptly canceled by the
Trustee. No Securities shall be authenticated in lieu of or in exchange for any
Securities canceled as provided in this Section, except as expressly permitted
by this Indenture. All canceled Securities held by the Trustee shall be disposed
of as directed by a Company Order.

SECTION 3.10 COMPUTATION OF INTEREST.

                  Except as otherwise specified as contemplated by Section 3.1
for Securities of any series, interest on the Securities of each series shall be
computed on the basis of a 360-day year of twelve 30-day months.


                                   ARTICLE IV

                           SATISFACTION AND DISCHARGE

SECTION 4.1 SATISFACTION AND DISCHARGE OF INDENTURE.

                  This Indenture shall upon Company Request cease to be of
further effect (except as to any surviving rights of registration of transfer or
exchange of Securities herein expressly provided for), and the Trustee, at the
expense of the Company, shall execute proper instruments acknowledging
satisfaction and discharge of this Indenture, when

                           (1) either

                                    (A) all Securities theretofore authenticated
                  and delivered (other than (i) Securities which have been
                  destroyed, lost or stolen and which have been replaced or paid
                  as provided in Section 3.6 and (ii) Securities for whose
                  payment money has theretofore been deposited in trust or
                  segregated and held in trust by the Trustee or the Company and
                  thereafter repaid to the Company or discharged from such
                  trust, as provided in Section 10.3) have been delivered to the
                  Trustee for cancellation; or

                                    (B) all such Securities not theretofore
                  delivered to the Trustee for cancellation

                                             (i) have become due and payable, or


                                       33
<PAGE>   41


                                             (ii) will become due and payable at
                  their Stated Maturity within one year, or

                                             (iii) are to be called for
                  redemption within one year under arrangements satisfactory to
                  the Trustee for the giving of notice of redemption by the
                  Trustee in the name, and at the expense, of the Company, and
                  the Company, in the case of (i), (ii) or (iii) above, has
                  deposited or caused to be deposited with the Trustee as trust
                  funds in trust for the purpose of making the following
                  payments, money in an amount sufficient to pay and discharge
                  the entire indebtedness on such Securities not theretofore
                  delivered to the Trustee for cancellation, for principal and
                  any premium and interest to the date of such deposit (in the
                  case of Securities which have become due and payable) or to
                  the Stated Maturity or Redemption Date, as the case may be;

                           (2) the Company has paid or caused to be paid all
         other sums payable hereunder by the Company; and

                           (3) the Company has delivered to the Trustee an
         Officers' Certificate and an Opinion of Counsel, each stating that all
         conditions precedent herein provided for relating to the satisfaction
         and discharge of this Indenture have been complied with.

                  Notwithstanding the satisfaction and discharge of this
Indenture, the obligations of the Company to the Trustee under Section 6.7, the
obligations of the Trustee to any Authenticating Agent under Section 6.14 and,
if money shall have been deposited with the Trustee pursuant to subclause (B) of
Clause (1) of this Section, the obligations of the Trustee under Section 4.2 and
the last paragraph of Section 10.3 shall survive.

SECTION 4.2 APPLICATION OF TRUST MONEY.

                  Subject to the provisions of the last paragraph of Section
10.3, all money deposited with the Trustee pursuant to Section 4.1 shall be held
in trust and applied by it, in accordance with the provisions of the Securities
and this Indenture, to the payment, either directly or through any Paying Agent
(including the Company acting as its own Paying Agent) as the Trustee may
determine, to the Persons entitled thereto, of the principal and any premium and
interest for whose payment such money has been deposited with the Trustee.


                                       34
<PAGE>   42


                                    ARTICLE V

                                    REMEDIES

SECTION 5.1 EVENTS OF DEFAULT.

                  "Event of Default," wherever used herein with respect to
Securities of any series, means any one of the following events (whatever the
reason for such Event of Default and whether it shall be occasioned by the
provisions of Article 15 or be voluntary or involuntary or be effected by
operation of law or pursuant to any judgment, decree or order of any court or
any order, rule or regulation of any administrative or governmental body):

                           (1) default in the payment of any interest upon any
         Security of that series when it becomes due and payable, and
         continuance of such default for a period of 30 days; or

                           (2) default in the payment of the principal of or any
         premium on any Security of that series at its Maturity; or

                           (3) default in the deposit of any sinking fund
         payment, when and as due by the terms of a Security of that series; or

                           (4) default in the performance, or breach, of any
         covenant or warranty of the Company in this Indenture (other than a
         covenant or warranty a default in whose performance or whose breach is
         elsewhere in this Section specifically dealt with or which has
         expressly been included in this Indenture solely for the benefit of
         series of Securities other than that series), and continuance of such
         default or breach for a period of 60 days after there has been given,
         by registered or certified mail, to the Company by the Trustee or to
         the Company and the Trustee by the Holders of at least 25% in principal
         amount of the Outstanding Securities of that series a written notice
         specifying such default or breach and requiring it to be remedied and
         stating that such notice is a "Notice of Default" hereunder; or

                           (5) the entry by a court having jurisdiction in the
         premises of a decree or order for relief in respect of the Company in
         an involuntary case or proceeding under any applicable Federal or State
         bankruptcy, insolvency, reorganization or other similar law or (B) a
         decree or order adjudging the company a bankrupt or insolvent, or
         approving as properly filed a petition seeking reorganization,


                                       35
<PAGE>   43


         arrangement, adjustment or composition of or in respect of the Company
         under any applicable Federal or State law, or appointing a custodian,
         receiver, liquidator, assignee, trustee, equestrator or other similar
         official of the Company or of any substantial part of its property, or
         ordering the winding up or liquidation of its affairs, and the
         continuance of any such decree or order for relief or any such other
         decree or order unstayed and in effect for a period of 90 consecutive
         days; or

                           (6) the commencement by the Company of a voluntary
         case or proceeding under any applicable Federal or State bankruptcy,
         insolvency, reorganization or other similar law or of any other case or
         proceeding to be adjudicated a bankrupt or insolvent, or the consent by
         it to the entry of a decree or order for relief in respect of the
         Company in an involuntary case or proceeding under any applicable
         Federal or State bankruptcy, insolvency, reorganization or other
         similar law or to the commencement of any bankruptcy or insolvency case
         or proceeding against it, or the filing by it of a petition or answer
         or consent seeking reorganization or relief under any applicable
         Federal or State law, or the consent by it to the filing of such
         petition or to the appointment of or taking possession by a custodian,
         receiver, liquidator, assignee, trustee, sequestrator or other similar
         official of the Company or of any substantial part of its property, or
         the making by it of an assignment for the benefit of creditors, or the
         admission by it in writing of its inability to pay its debts generally
         as they become due, or the taking of corporate action by the Company in
         furtherance of any such action; or

                           (7) any other Event of Default provided with respect
         to Securities of that series.

SECTION 5.2 ACCELERATION OF MATURITY; RESCISSION AND ANNULMENT.

                  If an Event of Default (other than an Event of Default
specified in Section 5.1(5) or 5.1(6)) with respect to Securities of any series
at the time Outstanding occurs and is continuing, then in every such case the
Trustee or the Holders of not less than 25% in principal amount of the
Outstanding Securities of that series may declare the principal amount of all
the Securities of that series (or, if any Securities of that series are Original
Issue Discount Securities, such portion of the principal amount of such
Securities as may be specified by the terms thereof) to be due and payable
immediately, by a notice in writing to the Company (and to the Trustee if given
by Holders), and upon any such declaration such principal amount (or specified
amount)


                                       36
<PAGE>   44

shall become immediately due and payable. If an Event of Default specified in
Section 5.1(5) or 5.1(6) with respect to Securities of any series at the time
Outstanding occurs, the principal amount of all the Securities of that series
(or, if any Securities of that series are Original Issue Discount Securities,
such portion of the principal amount of such Securities as may be specified by
the terms thereof) shall automatically, and without any declaration or other
action on the part of the Trustee or any Holder, become immediately due and
payable. Any payments by the Company on the Securities following any such
acceleration will be subject to the subordination provisions of Article 15 to
the extent provided therein.

                  At any time after such a declaration of acceleration with
respect to Securities of any series has been made and before a judgment or
decree for payment of the money due has been obtained by the Trustee as
hereinafter in this Article provided, the Holders of a majority in principal
amount of the Outstanding Securities of that series, by written notice to the
Company and the Trustee, may rescind and annul such declaration and its
consequences if

                           (1) the Company has paid or deposited with the
         Trustee a sum sufficient to pay

                                    (A) all overdue interest on all Securities
                  of that series,

                                    (B) the principal of (and premium, if any,
                  on) any Securities of that series which have become due
                  otherwise than by such declaration of acceleration and any
                  interest thereon at the rate or rates prescribed therefor in
                  such Securities,

                                    (C) to the extent that payment of such
                  interest is lawful, interest upon overdue interest at the rate
                  or rates prescribed therefor in such Securities, and

                                    (D) all sums paid or advanced by the Trustee
                  hereunder and the reasonable compensation, expenses,
                  disbursements and advances of the Trustee, its agents and
                  counsel; and

                           (2) all Events of Default with respect to Securities
         of that series, other than the non-payment of the principal of
         Securities of that series which have become due solely by such
         declaration of acceleration, have been cured or waived as provided in
         Section 5.13. No


                                       37
<PAGE>   45

         such rescission shall affect any subsequent default or impair any right
         consequent thereon.

SECTION 5.3   COLLECTION OF INDEBTEDNESS AND SUITS FOR
                    ENFORCEMENT BY TRUSTEE.

                  The Company covenants that if

                           (1) default is made in the payment of any interest on
         any Security when such interest becomes due and payable and such
         default continues for a period of 30 days, or

                           (2) default is made in the payment of the principal
         of (or premium, if any, on) any Security at the Maturity thereof, the
         Company will, upon demand of the Trustee, pay to it, for the benefit of
         the Holders of such Securities, the whole amount then due and payable
         on such Securities for principal and any premium and interest and, to
         the extent that payment of such interest shall be legally enforceable,
         interest on any overdue principal and premium and on any overdue
         interest, at the rate or rates prescribed therefor in such Securities,
         and, in addition thereto, such further amount as shall be sufficient to
         cover the costs and expenses of collection, including the reasonable
         compensation, expenses, disbursements and advances of the Trustee, its
         agents and counsel.

                  If an Event of Default with respect to Securities of any
series occurs and is continuing, the Trustee may in its discretion proceed to
protect and enforce its rights and the rights of the Holders of Securities of
such series by such appropriate judicial proceedings as the Trustee shall deem
most effectual to protect and enforce any such rights, whether for the specific
enforcement of any covenant or agreement in this Indenture or in aid of the
exercise of any power granted herein, or to enforce any other proper remedy.

SECTION 5.4 TRUSTEE MAY FILE PROOFS OF CLAIM.

                  In case of any judicial proceeding relative to the Company (or
any other obligor upon the Securities), its property or its creditors, the
Trustee shall be entitled and empowered, by intervention in such proceeding or
otherwise, to take any and all actions authorized under the Trust Indenture Act
in order to have claims of the Holders and the Trustee allowed in any such
proceeding. In particular, the Trustee shall be authorized 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,

                                       38
<PAGE>   46



trustee, liquidator, sequestrator or other 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 to 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 6.7.

                  No provision of this Indenture 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 Securities 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;
provided, however, that the Trustee may, on behalf of the Holders, vote for the
election of a trustee in bankruptcy or similar official and be a member of a
creditors' or other similar committee.

SECTION 5.5 TRUSTEE MAY ENFORCE CLAIMS WITHOUT POSSESSION OF SECURITIES.

                  All rights of action and claims under this Indenture or the
Securities may be prosecuted and enforced by the Trustee without the possession
of any of the Securities or the production thereof in any proceeding relating
thereto, and any such proceeding instituted by the Trustee shall be brought in
its own name as trustee of an express trust, and any recovery of judgment shall,
after provision for the payment of the reasonable compensation, expenses,
disbursements and advances of the Trustee, its agents and counsel, be for the
ratable benefit of the Holders of the Securities in respect of which such
judgment has been recovered.

SECTION 5.6   APPLICATION OF MONEY COLLECTED.

                  Any money collected by the Trustee pursuant to this Article
shall be applied in the following order, at the date or dates fixed by the
Trustee and, in case of the distribution of such money on account of principal
or any premium or interest, upon presentation of the Securities and the notation
thereon of the payment if only partially paid and upon surrender thereof if
fully paid:

                  FIRST: To the payment of all amounts due the Trustee under
Section 6.7;

                  SECOND: Subject to Article 15, to the payment of the amounts
then due and unpaid for principal of and any premium, if any, and interest on
the Securities in respect of which or for the benefit of which such money has
been collected, ratably,


                                       39
<PAGE>   47


without preference or priority of any kind, according to the amounts due and
payable on such Securities for principal and any premium, if any, and interest,
respectively; and

                  THIRD: The balance, if any, to the Company or any other Person
or Persons entitled thereto.


SECTION 5.7 LIMITATION ON SUITS.

                  No Holder of any Security of any series shall have any right
to institute any proceeding, judicial or otherwise, with respect to this
Indenture, or for the appointment of a receiver or trustee, or for any other
remedy hereunder, unless

                           (1) such Holder has previously given written notice
         to the Trustee of a continuing Event of Default with respect to the
         Securities of that series;

                           (2) the Holders of not less than 25% in principal
         amount of the Outstanding Securities of that series shall have made
         written request to the Trustee to institute proceedings in respect of
         such Event of Default in its own name as Trustee hereunder;

                           (3) such Holder or Holders have offered to the
         Trustee reasonable indemnity against the costs, expenses and
         liabilities to be incurred in compliance with such request;

                           (4) the Trustee for 60 days after its receipt of such
         notice, request and offer of indemnity has failed to institute any such
         proceeding; and

                           (5) no direction inconsistent with such written
         request has been given to the Trustee during such 60-day period by the
         Holders of a majority in principal amount of the Outstanding Securities
         of that series; it being understood and intended that no one or more of
         such Holders shall have any right in any manner whatever by virtue of,
         or by availing of, any provision of this Indenture to affect, disturb
         or prejudice the rights of any other of such Holders, or to obtain or
         to seek to obtain priority or preference over any other of such Holders
         or to enforce any right under this Indenture, except in the manner
         herein provided and for the equal and ratable benefit of all of such
         Holders.


                                       40
<PAGE>   48


SECTION 5.8   UNCONDITIONAL RIGHT OF HOLDERS TO RECEIVE
              PRINCIPAL, PREMIUM AND INTEREST AND TO CONVERT.

                  Notwithstanding any other provision in this Indenture, the
Holder of any Security shall have the right, which is absolute and
unconditional, to receive payment of the principal of and any premium and
(subject to Section 3.7) interest on such Security on the respective Stated
Maturities expressed in such Security (or, in the case of redemption, on the
Redemption Date), to convert such Securities in accordance with Article 14 to
the extent that such right to convert is applicable to such Security and to
institute suit for the enforcement of any such payment, and such rights shall
not be impaired without the consent of such Holder.

SECTION 5.9 RESTORATION OF RIGHTS AND REMEDIES.

                  If the Trustee or any Holder has instituted any proceeding to
enforce any right or remedy under this Indenture and such proceeding has been
discontinued or abandoned for any reason, or has been determined adversely to
the Trustee or to such Holder, then and in every such case, subject to any
determination in such proceeding, the Company, the Trustee and the Holders shall
be restored severally and respectively to their former positions hereunder and
thereafter all rights and remedies of the Trustee and the Holders shall continue
as though no such proceeding had been instituted.

SECTION 5.10 RIGHTS AND REMEDIES CUMULATIVE.

                  Except as otherwise provided with respect to the replacement
or payment of mutilated, destroyed, lost or stolen Securities in the last
paragraph of Section 3.6, no right or remedy herein conferred upon or reserved
to the Trustee or to the Holders is intended to be exclusive of any other right
or remedy, and every right and remedy shall, to the extent permitted by law, be
cumulative and in addition to every other right and remedy given hereunder or
now or hereafter existing at law or in equity or otherwise. The assertion or
employment of any right or remedy hereunder, or otherwise, shall not prevent the
concurrent assertion or employment of any other appropriate right or remedy.

SECTION 5.11 DELAY OR OMISSION NOT WAIVER.

                  No delay or omission of the Trustee or of any Holder of any
Securities to exercise any right or remedy accruing upon any Event of Default
shall impair any such right or remedy or constitute a waiver of any such Event
of Default or an acquiescence therein. Every right and remedy given by this
Article or by law to the Trustee or to the Holders may be exercised from time to
time, and as often as may be deemed expedient,


                                       41
<PAGE>   49


by the Trustee (subject to the limitations contained in this Indenture) or by
the Holders, as the case may be.

SECTION 5.12 CONTROL BY HOLDERS.

                  The Holders of a majority in principal amount of the
Outstanding Securities of any series shall have the right to direct the time,
method and place of conducting any proceeding for any remedy available to the
Trustee, or exercising any trust or power conferred on the Trustee, with respect
to the Securities of such series, provided that:

                           (1) such direction shall not be in conflict with any
         rule of law or with this Indenture and the Trustee shall not have
         determined that the action so directed would be unjustly prejudicial to
         Holders of Securities of that series, or any other series, not taking
         part in such direction; and

                           (2) the Trustee may take any other action deemed
         proper by the Trustee which is not inconsistent with such direction or
         this Indenture.

SECTION 5.13   WAIVER OF PAST DEFAULTS.

                  The Holders of not less than a majority in principal amount of
the Outstanding Securities of any series may on behalf of the Holders of all the
Securities of such series waive any past default hereunder with respect to such
series and its consequences, except:

                           (1) a default in the payment of the principal of or
         any premium or interest on any Security of such series; or

                           (2) to the extent such right is applicable to such
         Security, a failure by the Company on request to convert any Security
         into Common Stock; or

                           (3) in respect of a covenant or provision hereof
         which under Article 9 cannot be modified or amended without the consent
         of the Holder of each Outstanding Security of such series affected.

                  Upon any such waiver, such default shall cease to exist, and
any Event of Default arising therefrom shall be deemed to have been cured, for
every purpose of this


                                       42
<PAGE>   50


Indenture; but no such waiver shall extend to any subsequent or other default or
impair any right consequent thereon.

SECTION 5.14 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,
suffered or omitted by it as Trustee, a court may require any party litigant in
such suit to file an undertaking to pay the costs of such suit, and may assess
costs against any such party litigant, in the manner and to the extent provided
in the Trust Indenture Act; provided that neither this Section nor the Trust
Indenture Act shall be deemed to authorize any court to require such an
undertaking or to make such an assessment in any suit instituted by the Company
or in any suit for the enforcement of the right to convert any Security in
accordance with Article 14.

SECTION 5.15 WAIVER OF USURY, STAY OR EXTENSION LAWS.

                  The Company covenants (to the extent that it may lawfully do
so) that it will not at any time insist upon, or plead, or in any manner
whatsoever claim or take the benefit or advantage of, any usury, stay or
extension law wherever enacted, now or at any time hereafter in force, 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 will not hinder, delay or impede
the execution of any power herein granted to the Trustee, but will suffer and
permit the execution of every such power as though no such law had been enacted.


                                   ARTICLE VI

                                   THE TRUSTEE

SECTION 6.1 CERTAIN DUTIES AND RESPONSIBILITIES.

                  The duties and responsibilities of the Trustee shall be as
provided by the Trust Indenture Act. Notwithstanding the foregoing, no provision
of this Indenture shall require the Trustee to expend or risk its own funds or
otherwise incur any financial liability in the performance of any of its duties
hereunder, or in the exercise of any of its rights or powers if it shall have
reasonable grounds for believing that repayment of such funds or adequate
indemnity against such risk or liability is not reasonably assured to it.
Whether or not therein expressly so provided, every provision of this Indenture
relating

                                       43
<PAGE>   51


to the conduct or affecting the liability of or affording protection to the
Trustee shall be subject to the provisions of this Section.

SECTION 6.2 NOTICE OF DEFAULTS.

                  If a default occurs hereunder with respect to Securities of
any series, the Trustee shall give the Holders of Securities of such series
notice of such default as and to the extent provided by the Trust Indenture Act;
provided, however, that in the case of any default of the character specified in
Section 5.1(4) with respect to Securities of such series, no such notice to
Holders shall be given until at least 30 days after the occurrence thereof. For
the purpose of this Section, the term "default" means any event which is, or
after notice or lapse of time or both would become, an Event of Default with
respect to Securities of such series.

SECTION 6.3 CERTAIN RIGHTS OF TRUSTEE.

                  Subject to the provisions of Section 6.1:

                           (1) the Trustee may 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 believed by it to be genuine and to have
         been signed or presented by the proper party or parties;

                           (2) 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 shall be
         sufficiently evidenced by a Board Resolution;

                           (3) 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) is entitled to and may, in the absence of bad faith on its
         part, rely upon an Officers' Certificate;

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


                                       44
<PAGE>   52


                           (5) the Trustee shall be under no obligation to
         exercise any of the rights or powers vested in it by this Indenture at
         the request or direction of any of the Holders pursuant to this
         Indenture, unless such Holders shall have offered to the Trustee
         reasonable security or indemnity against the costs, expenses and
         liabilities which might be incurred by it in compliance with such
         request or direction;

                           (6) 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; and

                           (7) 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.

SECTION 6.4 NOT RESPONSIBLE FOR RECITALS OR ISSUANCE OF SECURITIES.

                  The recitals contained herein and in the Securities, except
the Trustee's certificates of authentication, shall be taken as the statements
of the Company, and neither the Trustee nor any Authenticating Agent assumes any
responsibility for their correctness. The Trustee makes no representations as to
the validity, sufficiency or priority of this Indenture or of the Securities.
Neither the Trustee nor any Authenticating Agent shall be accountable for the
use or application by the Company of Securities or the proceeds thereof.

SECTION 6.5 MAY HOLD SECURITIES AND ACT AS TRUSTEE UNDER OTHER INDENTURES.

                  The Trustee, any Authenticating Agent, any Paying Agent, any
Security Registrar or any other agent of the Company, in its individual or any
other capacity, may become the owner or pledgee of Securities and, subject to
Sections 6.8 and 6.13, may otherwise deal with the Company with the same rights
it would have if it were not Trustee, Authenticating Agent, Paying Agent,
Security Registrar or such other agent.


                                       45
<PAGE>   53


                  Subject to the limitations imposed by the Trust Indenture Act,
nothing in this Indenture shall prohibit the Trustee from becoming and acting as
trustee under other indentures under which other securities, or certificates of
interest of participation in other securities, of the Company are outstanding in
the same manner as if it were not Trustee hereunder.

SECTION 6.6 MONEY HELD IN TRUST.

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

SECTION 6.7   COMPENSATION AND REIMBURSEMENT.

                  The Company agrees:

                           (1) to pay to the Trustee from time to time
         reasonable compensation for all services rendered by it hereunder
         (which compensation shall not be limited by any provision of law in
         regard to the compensation of a trustee of an express trust);

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

                           (3) to indemnify the Trustee for, and to hold it
         harmless against, any loss, liability or expense incurred without
         negligence or bad faith on its part, arising out of or in connection
         with the acceptance or administration of the trust or trusts hereunder,
         including the costs and expenses of defending itself against any claim
         or liability in connection with the exercise or performance of any of
         its powers or duties hereunder.

SECTION 6.8 CONFLICTING INTERESTS.

                  If the Trustee has or shall acquire a conflicting interest
within the meaning of the Trust Indenture Act, the Trustee shall either
eliminate such interest or


                                       46
<PAGE>   54


resign, to the extent and in the manner provided by, and subject to the
provisions of, the Trust Indenture Act and this Indenture. To the extent
permitted by such Act, the Trustee shall not be deemed to have a conflicting
interest by virtue of being a trustee under this Indenture with respect to
Securities of more than one series.

SECTION 6.9 CORPORATE TRUSTEE REQUIRED; ELIGIBILITY.

                  There shall at all times be one (and only one) Trustee
hereunder with respect to the Securities of each series, which may be Trustee
hereunder for Securities of one or more other series. Each Trustee shall be a
Person that is eligible pursuant to the Trust Indenture Act to act as such and
has (or if the Trustee is a member of a bank holding company system, its bank
holding company has) a combined capital and surplus of at least $50,000,000. If
any such Person or bank holding company publishes reports of condition at least
annually, pursuant to law or to the requirements of its supervising or examining
authority, then for the purposes of this Section and to the extent permitted by
the Trust Indenture Act, the combined capital and surplus of such Person or bank
holding company shall be deemed to be its combined capital and surplus as set
forth in its most recent report of condition so published. If at any time the
Trustee with respect to the Securities of any series shall cease to be eligible
in accordance with the provisions of this Section, it shall resign immediately
in the manner and with the effect hereinafter specified in this Article.

SECTION 6.10 RESIGNATION AND REMOVAL; APPOINTMENT OF SUCCESSOR.

                  No resignation or removal of the Trustee and no appointment of
a successor Trustee pursuant to this Article shall become effective until the
acceptance of appointment by the successor Trustee in accordance with the
applicable requirements of Section 6.11.

                  The Trustee may resign at any time with respect to the
Securities of one or more series by giving written notice thereof to the
Company. If the instrument of acceptance by a successor Trustee required by
Section 6.11 shall not have been delivered to the Trustee within 30 days after
the giving of such notice of resignation, the resigning Trustee may petition any
court of competent jurisdiction for the appointment of a successor Trustee with
respect to the Securities of such series.

                  The Trustee may be removed at any time with respect to the
Securities of any series by Act of the Holders of a majority in principal amount
of the Outstanding Securities of such series, delivered to the Trustee and to
the Company.


                                       47
<PAGE>   55


                  If at any time:

                           (1) the Trustee shall fail to comply with Section 6.8
         after written request therefor by the Company or by any Holder who has
         been a bona fide Holder of a Security for at least six months, or


                           (2) the Trustee shall cease to be eligible under
         Section 6.9 and shall fail to resign after written request therefor by
         the Company or by any such Holder, or

                           (3) the Trustee shall become incapable of acting or
         shall be adjudged a bankrupt or insolvent or a receiver of the Trustee
         or of its property shall be appointed or any public officer shall take
         charge or control of the Trustee or of its property or affairs for the
         purpose of rehabilitation, conservation or liquidation, then, in any
         such case, (A) the Company by a Board Resolution may remove the Trustee
         with respect to all Securities, or (B) subject to Section 5.14, any
         Holder who has been a bona fide Holder of a Security for at least six
         months may, on behalf of himself and all others similarly situated,
         petition any court of competent jurisdiction for the removal of the
         Trustee with respect to all Securities and the appointment of a
         successor Trustee or Trustees.

                  If the Trustee shall resign, be removed or become incapable of
acting, or if a vacancy shall occur in the office of Trustee for any cause, with
respect to the Securities of one or more series, the Company, by a Board
Resolution, shall promptly appoint a successor Trustee or Trustees with respect
to the Securities of that or those series (it being understood that any such
successor Trustee may be appointed with respect to the Securities of one or more
or all of such series and that at any time there shall be only one Trustee with
respect to the Securities of any particular series) and shall comply with the
applicable requirements of Section 6.11. If, within one year after such
resignation, removal or incapability, or the occurrence of such vacancy, a
successor Trustee with respect to the Securities of any series shall be
appointed by Act of the Holders of a majority in principal amount of the
Outstanding Securities of such series delivered to the Company and the retiring
Trustee, the successor Trustee so appointed shall, forthwith upon its acceptance
of such appointment in accordance with the applicable requirements of Section
6.11, become the successor Trustee with respect to the Securities of such series
and to that extent supersede the successor Trustee appointed by the Company. If
no successor Trustee with respect to the Securities of any series shall have
been so appointed by the Company or the Holders and accepted appointment in the
manner required by Section 6.11, the retiring Trustee may petition, or any
Holder who has been a bona fide Holder of a Security of such series for at least
six months may, on behalf of himself and all others similarly situated, petition
any court of competent jurisdiction for the appointment of a successor Trustee
with respect to the Securities of such series.


                                       48
<PAGE>   56


                  The Company shall give notice of each resignation and each
removal of the Trustee with respect to the Securities of any series and each
appointment of a successor Trustee with respect to the Securities of any series
to all Holders of Securities of such series in the manner provided in Section
1.6. Each notice shall include the name of the successor Trustee with respect to
the Securities of such series and the address of its Corporate Trust Office.

SECTION 6.11 ACCEPTANCE OF APPOINTMENT BY SUCCESSOR.

                  In case of the appointment hereunder of a successor Trustee
with respect to all Securities, every such successor Trustee so appointed shall
execute, acknowledge and deliver to the Company and to the retiring Trustee an
instrument accepting such appointment, and thereupon the resignation or removal
of the retiring Trustee shall become effective and such successor Trustee,
without any further act, deed or conveyance, shall become vested with all the
rights, powers, trusts and duties of the retiring Trustee; but, on the request
of the Company or the successor Trustee, such retiring Trustee shall, upon
payment of its charges, execute and deliver an instrument transferring to such
successor Trustee all the rights, powers and trusts of the retiring Trustee and
shall duly assign, transfer and deliver to such successor Trustee all property
and money held by such retiring Trustee hereunder.

                  In case of the appointment hereunder of a successor Trustee
with respect to the Securities of one or more (but not all) series, the Company,
the retiring Trustee and each successor Trustee with respect to the Securities
of one or more series shall execute and deliver an indenture supplemental hereto
wherein each successor Trustee shall accept such appointment and which (1) shall
contain such provisions as shall be necessary or desirable to transfer and
confirm to, and to vest in, each successor Trustee all the rights, powers,
trusts and duties of the retiring Trustee with respect to the Securities of that
or those series to which the appointment of such successor Trustee relates, (2)
if the retiring Trustee is not retiring with respect to all Securities, shall
contain such provisions as shall be deemed necessary or desirable to confirm
that all the rights, powers, trusts and duties of the retiring Trustee with
respect to the Securities of that or those series as to which the retiring
Trustee is not retiring shall continue to be vested in the retiring Trustee, and
(3) shall add to or change any of the provisions of this Indenture as shall be
necessary to provide for or facilitate the administration of the trusts
hereunder by more than one Trustee, it being understood that nothing herein or
in such supplemental indenture shall constitute such Trustees co-trustees of the
same trust and that each such Trustee shall be trustee of a trust or trusts
hereunder separate and apart from any trust or trusts hereunder administered by
any other such Trustee; and upon the execution and delivery of such supplemental
indenture the resignation or removal of the retiring Trustee shall become
effective to the extent provided therein and each such successor Trustee,
without any further act, deed or conveyance, shall become


                                       49
<PAGE>   57


vested with all the rights, powers, trusts and duties of the retiring Trustee
with respect to the Securities of that or those series to which the appointment
of such successor Trustee relates; but, on request of the Company or any
successor Trustee, such retiring Trustee shall duly assign, transfer and deliver
to such successor Trustee all property and money held by such retiring Trustee
hereunder with respect to the Securities of that or those series to which the
appointment of such successor Trustee relates.

                  Upon request of any such successor Trustee, the Company shall
execute any and all instruments for more fully and certainly vesting in and
confirming to such successor Trustee all such rights, powers and trusts referred
to in the first or second preceding paragraph, as the case may be.

                  No successor Trustee shall accept its appointment unless at
the time of such acceptance such successor Trustee shall be qualified and
eligible under this Article.

SECTION 6.12 MERGER, CONVERSION, CONSOLIDATION OR SUCCESSION TO BUSINESS.

                  Any corporation into which the Trustee may be merged or
converted or with which it may be consolidated, or any corporation resulting
from any merger, conversion or consolidation to which the Trustee shall be a
party, or any corporation succeeding to all or substantially all the corporate
trust business of the Trustee, shall be the successor of the Trustee hereunder,
provided such corporation shall be otherwise qualified and eligible under this
Article, without the execution or filing of any paper or any further act on the
part of any of the parties hereto. In case any Securities shall have been
authenticated, but not delivered, by the Trustee then in office, any successor
by merger, conversion or consolidation to such authenticating Trustee may adopt
such authentication and deliver the Securities so authenticated with the same
effect as if such successor Trustee had itself authenticated such Securities.

SECTION 6.13 PREFERENTIAL COLLECTION OF CLAIMS AGAINST COMPANY.

                  If and when the Trustee shall be or become a creditor of the
Company (or any other obligor upon the Securities), the Trustee shall be subject
to the provisions of the Trust Indenture Act regarding the collection of claims
against the Company (or any such other obligor).


                                       50
<PAGE>   58


SECTION 6.14 APPOINTMENT OF AUTHENTICATING AGENT.

                  The Trustee may appoint an Authenticating Agent or Agents with
respect to one or more series of Securities which shall be authorized to act on
behalf of the Trustee to authenticate Securities of such series issued upon
original issue and upon exchange, registration of transfer or partial redemption
thereof or pursuant to Section 3.6, and Securities so authenticated shall be
entitled to the benefits of this Indenture and shall be valid and obligatory for
all purposes as if authenticated by the Trustee hereunder. Wherever reference is
made in this Indenture to the authentication and delivery of Securities by the
Trustee or the Trustee's certificate of authentication, such reference shall be
deemed to include authentication and delivery on behalf of the Trustee by an
Authenticating Agent and a certificate of authentication executed on behalf of
the Trustee by an Authenticating Agent. Each Authenticating Agent shall be
acceptable to the Company and shall at all times be a corporation organized and
doing business under the laws of the United States of America, any State thereof
or the District of Columbia, authorized under such laws to act as Authenticating
Agent, having (or if the Authenticating Agent is a member of a bank holding
company system, its bank holding company has) a combined capital and surplus of
not less than $50,000,000 and subject to supervision or examination by Federal
or State authority. If such Authenticating Agent publishes reports of condition
at least annually, pursuant to law or to the requirements of said supervising or
examining authority, then for the purposes of this Section, the combined capital
and surplus of such Authenticating Agent shall be deemed to be its combined
capital and surplus as set forth in its most recent report of condition so
published. If at any time an Authenticating Agent shall cease to be eligible in
accordance with the provisions of this Section, such Authenticating Agent shall
resign immediately in the manner and with the effect specified in this Section.

                  Any corporation into which an Authenticating Agent may be
merged or converted or with which it may be consolidated, or any corporation
resulting from any merger, conversion or consolidation to which such
Authenticating Agent shall be a party, or any corporation succeeding to the
corporate agency or corporate trust business of an Authenticating Agent, shall
continue to be an Authenticating Agent, provided such corporation shall be
otherwise eligible under this Section, without the execution or filing of any
paper or any further act on the part of the Trustee or the Authenticating Agent.

                  An Authenticating Agent may resign at any time by giving
written notice thereof to the Trustee and to the Company. The Trustee may at any
time terminate the agency of an Authenticating Agent by giving written notice
thereof to such Authenticating Agent and to the Company. Upon receiving such a
notice of resignation or upon such a termination, or in case at any time such
Authenticating Agent shall cease to be eligible in accordance with the
provisions of this Section, the Trustee may appoint a successor Authenticating
Agent which shall be acceptable to the Company and shall give notice of such
appointment in the manner provided in Section 1.6 to all Holders of


                                       51
<PAGE>   59


Securities of the series with respect to which such Authenticating Agent will
serve. Any successor Authenticating Agent upon acceptance of its appointment
hereunder shall become vested with all the rights, powers and duties of its
predecessor hereunder, with like effect as if originally named as an
Authenticating Agent. No successor Authenticating Agent shall be appointed
unless eligible under the provisions of this Section.

                  The Trustee agrees to pay to each Authenticating Agent from
time to time reasonable compensation for its services under this Section, and
the Trustee shall be entitled to be reimbursed for such payments, subject to the
provisions of Section 6.7.

                  If an appointment with respect to one or more series is made
pursuant to this Section 6.12, the Securities of such series may have endorsed
thereon, in addition to the Trustee's certificate of authentication, an
alternative certificate of authentication in the following form:

                  This is one of the Securities of the series designated therein
referred to in the within-mentioned Indenture.

                                            [                     ],
                                             ---------------------
                                              as Trustee

                                            By:
                                               ------------------------
                                                As Authenticating Agent


                                            By:
                                               ------------------------
                                                  Authorized Officer


                                       52
<PAGE>   60
                                   ARTICLE VII

                HOLDERS' LISTS AND REPORTS BY TRUSTEE AND COMPANY

SECTION 7.1 COMPANY TO FURNISH TRUSTEE NAMES AND ADDRESSES OF HOLDERS.

                  The Company will furnish or cause to be furnished to the
Trustee:

                           (1) semi-annually, not later than 15 days after the
         Regular Record Date, a list, in such form as the Trustee may reasonably
         require, of the names and addresses of the Holders of Securities of
         each series as of such Regular Record Date, as the case may be; and

                           (2) at such other times as the Trustee may request in
         writing, within 30 days after the receipt by the Company of any such
         request, a list of similar form and content as of a date not more than
         15 days prior to the time such list is furnished; provided that no such
         list need be furnished by the Company to the Trustee so long as the
         Trustee is acting as Security Registrar.

SECTION 7.2 PRESERVATION OF INFORMATION; COMMUNICATIONS TO HOLDERS.

                  The Trustee shall preserve, in as current a form as is
reasonably practicable, the names and addresses of Holders contained in the most
recent list furnished to the Trustee as provided in Section 7.1 and the names
and addresses of Holders received by the Trustee in its capacity as Security
Registrar. The Trustee may destroy any list furnished to it as provided in
Section 7.1 upon receipt of a new list so furnished.

                  The rights of Holders to communicate with other Holders with
respect to their rights under this Indenture or under the Securities, and the
corresponding rights and privileges of the Trustee, shall be as provided by the
Trust Indenture Act.

                  Every Holder of Securities, by receiving and holding the same,
agrees with the Company and the Trustee that neither the Company nor the Trustee
nor any agent of either of them shall be held accountable by reason of any
disclosure of information as to names and addresses of Holders made pursuant to
the Trust Indenture Act.


                                       53
<PAGE>   61


SECTION 7.3 REPORTS BY TRUSTEE.

                  The Trustee shall transmit to Holders such reports concerning
the Trustee and its actions under this Indenture as may be required pursuant to
the Trust Indenture Act at the times and in the manner provided pursuant
thereto.

                  Reports so required to be transmitted at stated intervals of
not more than 12 months shall be transmitted no later than July 1 in each
calendar year, commencing with the first July 1 after the first issuance of
Securities pursuant to this Indenture.

                  A copy of each such report shall, at the time of such
transmission to Holders, be filed by the Trustee with each stock exchange upon
which any Securities are listed, with the Commission and with the Company. The
Company will notify the Trustee when any Securities are listed on any stock
exchange.

SECTION 7.4 REPORTS BY COMPANY.

                  The Company shall file with the Trustee and the Commission,
and transmit to Holders, such information, documents and other reports, and such
summaries thereof, as may be required pursuant to the Trust Indenture Act at the
times and in the manner provided pursuant to the Trust Indenture Act; provided
that any such information, documents or reports required to be filed with the
Commission pursuant to Section 13 or 15(d) of the Exchange Act shall be filed
with the Trustee within 15 days after the same is so required to be filed with
the Commission.


                                  ARTICLE VIII

              CONSOLIDATION, MERGER, CONVEYANCE, TRANSFER OR LEASE

SECTION 8.1 COMPANY MAY CONSOLIDATE, ETC., ONLY ON CERTAIN TERMS.

                  The Company shall not consolidate with or merge into any other
Person (in a transaction in which the Company is not the surviving corporation)
or convey, transfer or lease its properties and assets substantially as an
entirety to any Person, unless:

                           (1) in case the Company shall consolidate with or
         merge into another Person (in a transaction in which the Company is not
         the surviving corporation) or convey, transfer or lease its properties
         and assets substantially as an entirety to any Person, the Person
         formed by such consolidation or into which the Company is merged or the
         Person


                                       54
<PAGE>   62


         which acquires by conveyance or transfer, or which leases, the
         properties and assets of the Company substantially as an entirety shall
         be a corporation, limited liability company, partnership or trust,
         shall be organized and validly existing under the laws of the United
         States of America, any State thereof or the District of Columbia and
         shall expressly assume, by an indenture supplemental hereto, executed
         and delivered to the Trustee, in form satisfactory to the Trustee, the
         due and punctual payment of the principal of and any premium and
         interest on all the Securities and the performance or observance of
         every covenant of this Indenture on the part of the Company to be
         performed or observed and the conversion rights shall be provided for
         in accordance with Article 14, if applicable, or as otherwise specified
         pursuant to Section 3.1, by supplemental indenture satisfactory in form
         to the Trustee, executed and delivered to the Trustee, by the Person
         (if other than the Company) formed by such consolidation or into which
         the Company shall have been merged or by the Person which shall have
         acquired the Company's assets;

                           (2) immediately after giving effect to such
         transaction and treating any indebtedness which becomes an obligation
         of the Company or any Subsidiary as a result of such transaction as
         having been incurred by the Company or such Subsidiary at the time of
         such transaction, no Event of Default, and no event which, after notice
         or lapse of time or both, would become an Event of Default, shall have
         happened and be continuing; and

                           (3) the Company has delivered to the Trustee an
         Officers' Certificate and an Opinion of Counsel, each stating that such
         consolidation, merger, conveyance, transfer or lease and, if a
         supplemental indenture is required in connection with such transaction,
         such supplemental indenture comply with this Article and that all
         conditions precedent herein provided for relating to such transaction
         have been complied with.

SECTION 8.2 SUCCESSOR SUBSTITUTED.

                  Upon any consolidation of the Company with, or merger of the
Company into, any other Person or any conveyance, transfer or lease of the
properties and assets of the Company substantially as an entirety in accordance
with Section 8.1, the successor Person formed by such consolidation or into
which the Company is merged or to which such conveyance, transfer or lease is
made shall succeed to, and be substituted for, and may exercise every right and
power of, the Company under this


                                       55
<PAGE>   63


Indenture with the same effect as if such successor Person had been named as the
Company herein, and thereafter, except in the case of a lease, the predecessor
Person shall be relieved of all obligations and covenants under this Indenture
and the Securities.

                                   ARTICLE IX

                             SUPPLEMENTAL INDENTURES

SECTION 9.1 SUPPLEMENTAL INDENTURES WITHOUT CONSENT OF HOLDERS.

                  Without the consent of any Holders, the Company, when
authorized by a Board Resolution, and the Trustee, at any time and from time to
time, may enter into one or more indentures supplemental hereto, in form
satisfactory to the Trustee, for any of the following purposes:

                           (1) to evidence the succession of another Person to
         the Company, or successive successions, and the assumption by any such
         successor of the covenants of the Company herein and in the Securities;
         or

                           (2) to add to the covenants of the Company for the
         benefit of the Holders of all or any series of Securities (and if such
         covenants are to be for the benefit of less than all series of
         Securities, stating that such covenants are expressly being included
         solely for the benefit of such series) or to surrender any right or
         power herein conferred upon the Company; or

                           (3) to add any additional Events of Default for the
         benefit of the Holders of all or any series of Securities (and if such
         additional Events of Default are to be for the benefit of less than all
         series of Securities, stating that such additional Events of Default
         are expressly being included solely for the benefit of such series); or

                           (4) to add to or change any of the provisions of this
         Indenture to such extent as shall be necessary to permit or facilitate
         the issuance of Securities in bearer form, registrable or not
         registrable as to principal, and with or without interest coupons, or
         to permit or facilitate the issuance of Securities in uncertificated
         form; or


                                       56
<PAGE>   64

                           (5) to add to, change or eliminate any of the
         provisions of this Indenture in respect of one or more series of
         Securities, provided that any such addition, change or elimination (A)
         shall neither (i) apply to any Security of any series created prior to
         the execution of such supplemental indenture and entitled to the
         benefit of such provision nor (ii) modify the rights of the Holder of
         any such Security with respect to such provision or (B) shall become
         effective only when there is no such Security Outstanding; or

                           (6) to secure the Securities; or

                           (7) to establish the form or terms of Securities of
         any series as permitted by Sections 2.1 and 3.1; or

                           (8) to evidence and provide for the acceptance of
         appointment hereunder by a successor Trustee with respect to the
         Securities of one or more series and to add to or change any of the
         provisions of this Indenture as shall be necessary to provide for or
         facilitate the administration of the trusts hereunder by more than one
         Trustee, pursuant to the requirements of Section 6.11; or

                           (9) to make provision with respect to the conversion
         rights of Holders pursuant to the requirements of Article 14, including
         providing for the conversion of the securities into any security (other
         than the Common Stock of the Company) or property of the Company; or

                           (10) to cure any ambiguity, to correct or supplement
         any provision herein which may be defective or inconsistent with any
         other provision herein, or to make any other provisions with respect to
         matters or questions arising under this Indenture, provided that such
         action pursuant to this Clause (10) shall not adversely affect the
         interests of the Holders of Securities of any series in any material
         respect; or

                           (11) to supplement any of the provisions of the
         Indenture to such extent as shall be necessary to permit or facilitate
         the defeasance and discharge of any series of Securities pursuant to
         Articles Four and Thirteen, provided that any such action shall not
         adversely affect the interests of the Holders of Securities of such
         series or any other series of Securities in any material respect.


                                       57
<PAGE>   65

SECTION 9.2 SUPPLEMENTAL INDENTURES WITH CONSENT OF HOLDERS.

                  With the consent of the Holders of a majority in principal
amount of the Outstanding Securities of each series affected by such
supplemental indenture, by Act of said Holders delivered to the Company and the
Trustee, the Company, when authorized by a Board Resolution, and the Trustee may
enter into an indenture or indentures supplemental hereto for the purpose of
adding any provisions to or changing in any manner or eliminating any of the
provisions of this Indenture or of modifying in any manner the rights of the
Holders of Securities of such series under this Indenture; provided, however,
that no such supplemental indenture shall, without the consent of the Holder of
each Outstanding Security affected thereby,

                           (1) change the Stated Maturity of the principal of,
         or any installment of principal of or interest on, any Security, or
         reduce the principal amount thereof or the rate of interest thereon or
         any premium payable upon the redemption thereof, or reduce the amount
         of the principal of an Original Issue Discount Security or any other
         Security which would be due and payable upon a declaration of
         acceleration of the Maturity thereof pursuant to Section 5.2, or change
         any Place of Payment where, or the coin or currency in which, any
         Security or any premium or interest thereon is payable, or impair the
         right to institute suit for the enforcement of any such payment on or
         after the Stated Maturity thereof (or, in the case of redemption, on or
         after the Redemption Date), or modify the provisions of this Indenture
         with respect to the subordination of such series of Securities in a
         manner adverse to the Holders of Securities of such series, or, in the
         case of securities of any series that are convertible into Securities
         or other securities of the Company, adversely affect the right of
         Holders to convert any of the Securities of such series other than as
         provided in or pursuant to this Indenture, or

                           (2) reduce the percentage in principal amount of the
         Outstanding Securities of any series, the consent of whose Holders is
         required for any such supplemental indenture, or the consent of whose
         Holders is required for any waiver (of compliance with certain
         provisions of this Indenture or certain defaults hereunder and their
         consequences) provided for in this Indenture, or

                           (3) modify any of the provisions of this Section,
         Section 5.13 or Section 10.06, except to increase any such percentage
         or to provide that certain other provisions of this Indenture cannot be
         modified or waived without the consent of the Holder of each
         Outstanding Security affected thereby; provided, however, that this
         clause shall not be deemed to require the consent of any Holder with


                                       58
<PAGE>   66


         respect to changes in the references to "the Trustee" and concomitant
         changes in this Section and Section 10.6, or the deletion of this
         proviso, in accordance with the requirements of Sections 6.11 and
         9.1(8), or

                           (4) if applicable, make any change that adversely
         affects the right to convert any security as provided in Article 14 or
         pursuant to Section 3.1 (except as permitted by Section 9.1(9)) or
         decrease the conversion rate or increase the conversion price of any
         such security. A supplemental indenture which changes or eliminates any
         covenant or other provision of this Indenture which has expressly been
         included solely for the benefit of one or more particular series of
         Securities, or which modifies the rights of the Holders of Securities
         of such series with respect to such covenant or other provision, shall
         be deemed not to affect the rights under this Indenture of the Holders
         of Securities of any other series.

It shall not be necessary for any Act of Holders under this Section to approve
the particular form of any proposed supplemental indenture, but it shall be
sufficient if such Act shall approve the substance thereof.

SECTION 9.3 EXECUTION OF SUPPLEMENTAL INDENTURES.

                  In executing, or accepting the additional trusts created by,
any supplemental indenture permitted by this Article or the modifications
thereby of the trusts created by this Indenture, the Trustee shall be entitled
to receive, and (subject to Sections 6.1 and 6.3) shall be fully protected in
relying upon, an Opinion of Counsel stating that the execution of such
supplemental indenture is authorized or permitted by this Indenture. The Trustee
may, but shall not be obligated to, enter into any such supplemental indenture
which affects the Trustee's own rights, duties or immunities under this
Indenture or otherwise.

SECTION 9.4 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 a part of this Indenture for all purposes; and
every Holder of Securities theretofore or thereafter authenticated and delivered
hereunder shall be bound thereby.


                                       59
<PAGE>   67


SECTION 9.5 CONFORMITY WITH TRUST INDENTURE ACT.

                  Every supplemental indenture executed pursuant to this Article
shall conform to the requirements of the Trust Indenture Act.

SECTION 9.6 REFERENCE IN SECURITIES TO SUPPLEMENTAL INDENTURES.

                  Securities of any series authenticated and delivered after the
execution of any supplemental indenture pursuant to this Article 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 of any series so modified as to conform, in the
opinion of the Trustee and the Company, 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 of such series.

SECTION 9.7 SUBORDINATION UNIMPAIRED.

                  No provision in any supplemental indenture which affects the
superior priority of the holders of Senior Indebtedness shall be effective
against holders of Senior Indebtedness.


                                    ARTICLE X

                                    COVENANTS

SECTION 10.1 PAYMENT OF PRINCIPAL, PREMIUM AND INTEREST.

                  The Company covenants and agrees for the benefit of each
series of Securities that it will duly and punctually pay the principal of and
any premium and interest on the Securities of that series in accordance with the
terms of the Securities and this Indenture.

SECTION 10.2 MAINTENANCE OF OFFICE OR AGENCY.

                  The Company will maintain in each Place of Payment for any
series of Securities an office or agency where Securities of that series may be
presented or surrendered for payment, where Securities of that series may be
surrendered for registration of transfer or exchange, where Securities of that
series may be surrendered for conversion and where notices and demands to or
upon the Company in respect of the Securities of that series and this Indenture
may be served. The Company will give prompt written notice to the Trustee of the
location, and any change in the location, of such office or agency. If at any
time the Company shall fail to maintain any such


                                       60
<PAGE>   68


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 Corporate Trust Office of the Trustee, and the Company hereby
appoints the Trustee as its agent to receive all such presentations, surrenders,
notices and demands. Unless otherwise provided in a supplemental indenture or
pursuant to Section 3.1 hereof, the Place of Payment for any series of
Securities shall be the Corporate Trust Office of the Trustee.

                  The Company may also from time to time designate one or more
other offices or agencies where the Securities of one or more series 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 each Place of Payment for Securities of any series for
such purposes. The Company will give prompt written notice to the Trustee of any
such designation or rescission and of any change in the location of any such
other office or agency.

SECTION 10.3 MONEY FOR SECURITIES PAYMENTS TO BE HELD IN TRUST.

                  If the Company shall at any time act as its own Paying Agent
with respect to any series of Securities, it will, on or before each due date of
the principal of or any premium or interest on any of the Securities of that
series, segregate and hold in trust for the benefit of the Persons entitled
thereto a sum sufficient to pay the principal and any premium and interest so
becoming due until such sums shall be paid to such Persons or otherwise disposed
of as herein provided and will promptly notify the Trustee of its action or
failure so to act.

                  Whenever the Company shall have one or more Paying Agents for
any series of Securities, it will, on or prior to each due date of the principal
of or any premium or interest on any Securities of that series, deposit with a
Paying Agent a sum sufficient to pay such amount, such sum to be held as
provided by the Trust Indenture Act, and (unless such Paying Agent is the
Trustee) the Company will promptly notify the Trustee of its action or failure
so to act.

                  The Company will cause each Paying Agent for any series of
Securities other than the Trustee to execute and deliver to the Trustee an
instrument in which such Paying Agent shall agree with the Trustee, subject to
the provisions of this Section, that such Paying Agent will (1) comply with the
provisions of the Trust Indenture Act applicable to it as a Paying Agent and (2)
during the continuance of any default by the Company (or any other obligor upon
the Securities of that series) in the making of any payment in respect of the
Securities of that series, upon the written request of the


                                       61
<PAGE>   69


Trustee, forthwith pay to the Trustee all sums held in trust by such Paying
Agent for payment in respect of the Securities of that series.

                  The Company may at any time, for the purpose of obtaining the
satisfaction and discharge of this Indenture or for any other purpose, pay, or
by Company Order direct any Paying Agent to pay, to the Trustee all sums held in
trust by the Company or such Paying Agent, such sums to be held by the Trustee
upon the same trusts as those upon which such sums were held by the Company or
such Paying Agent; and, upon such payment by any Paying Agent to the Trustee,
such Paying Agent shall be released from all further liability with respect to
such money.

                  Any money deposited with the Trustee or any Paying Agent, or
then held by the Company, in trust for the payment of the principal of or any
premium or interest on any Security of any series and remaining unclaimed for a
period ending on the earlier of the date that is ten Business Days prior to the
date such money would escheat to the State or two years after such principal,
premium or interest has become due and payable shall be paid to the Company on
Company Request, or (if then held by the Company) shall be discharged from such
trust; and the Holder of such Security shall thereafter, as an unsecured general
creditor, look only to the Company for payment thereof, and all liability of the
Trustee or such Paying Agent with respect to such trust money, and all liability
of the Company as trustee thereof, shall thereupon cease; provided, however,
that the Trustee or such Paying Agent, before being required to make any such
repayment, may at the expense of the Company cause to be published once, in a
newspaper published in the English language, customarily published on each
Business Day and of general circulation in each Place of Payment, notice that
such money remains unclaimed and that, after a date specified therein, which
shall not be less than 30 days from the date of such publication, any unclaimed
balance of such money then remaining will be repaid to the Company.

SECTION 10.4 STATEMENT BY OFFICERS AS TO DEFAULT.

                  The Company will deliver to the Trustee, within 120 days after
the end of each fiscal year of the Company ending after the date hereof, an
Officers' Certificate, stating whether or not to the best knowledge of the
signers thereof the Company is in default in the performance and observance of
any of the terms, provisions and conditions of this Indenture (without regard to
any period of grace or requirement of notice provided hereunder) and, if the
Company shall be in default, specifying all such defaults and the nature and
status thereof of which they may have knowledge. The fiscal year of the Company
currently ends on December 31; and the Company will give the Trustee prompt
written notice of any change of its fiscal year.


                                       62
<PAGE>   70

SECTION 10.5 EXISTENCE.

                  Subject to Article 8, the Company will do or cause to be done
all things necessary to preserve and keep in full force and effect its
existence.

SECTION 10.6 WAIVER OF CERTAIN COVENANTS.

                  Except as otherwise specified as contemplated by Section 3.1
for Securities of such series, the Company may, with respect to the Securities
of any series, omit in any particular instance to comply with any term,
provision or condition set forth in any covenant provided pursuant to Section
3.1(20) or 9.1(2) for the benefit of the Holders of such series if before the
time for such compliance the Holders of at least a majority in principal amount
of the Outstanding Securities of such series shall, by Act of such Holders,
either waive such compliance in such instance or generally waive compliance with
such term, provision or condition, but no such waiver shall extend to or affect
such term, provision or condition except to the extent so expressly waived, and,
until such waiver shall become effective, the obligations of the Company and the
duties of the Trustee in respect of any such term, provision or condition shall
remain in full force and effect.


                                   ARTICLE XI

                            REDEMPTION OF SECURITIES

SECTION 11.1 APPLICABILITY OF ARTICLE.

                  Securities of any series which are redeemable before their
Stated Maturity shall be redeemable in accordance with their terms and (except
as otherwise specified as contemplated by Section 3.1 for such Securities) in
accordance with this Article.

SECTION 11.2 ELECTION TO REDEEM; NOTICE TO TRUSTEE.

                  The election of the Company to redeem any Securities shall be
evidenced by a Board Resolution or in another manner specified as contemplated
by Section 3.1 for such Securities. In case of any redemption at the election of
the Company of less than all the Securities of any series (including any such
redemption affecting only a single Security), the Company shall, at least 45
days prior to the Redemption Date fixed by the Company (unless a shorter notice
shall be satisfactory to the Trustee), notify the Trustee of such Redemption
Date, of the principal amount of Securities of such series to be redeemed and,
if applicable, of the tenor of the Securities to be redeemed. In the case of any
redemption of Securities prior to the expiration of any restriction on such
redemption provided in the terms of such Securities or


                                       63
<PAGE>   71


elsewhere in this Indenture, the Company shall furnish the Trustee with an
Officers' Certificate evidencing compliance with such restriction.

SECTION 11.3 SELECTION BY TRUSTEE OF SECURITIES TO BE REDEEMED.

                  If less than all the Securities of any series are to be
redeemed (unless all the Securities of such series and of a specified tenor are
to be redeemed or unless such redemption affects only a single Security), the
particular Securities to be redeemed shall be selected not more than 45 days
prior to the Redemption Date by the Trustee, from the Outstanding Securities of
such series not previously called for redemption, by lot, or in the Trustee's
discretion, on a pro-rata basis, provided that the unredeemed portion of the
principal amount of any Security shall be in an authorized denomination (which
shall not be less than the minimum authorized denomination) for such Security.
If less than all the Securities of such series and of a specified tenor are to
be redeemed (unless such redemption affects only a single Security), the
particular Securities to be redeemed shall be selected not more than 45 days
prior to the Redemption Date by the Trustee, from the Outstanding Securities of
such series and specified tenor not previously called for redemption in
accordance with the preceding sentence.

                  If any Security selected for partial redemption is converted
in part before termination of the conversion right with respect to the portion
of the Security so selected, the converted portion of such Security shall be
deemed (so far as may be) to be the portion selected for redemption. Securities
which have been converted during a selection of Securities to be redeemed shall
be treated by the Trustee as Outstanding for the purpose of such selection.

                  The Trustee shall promptly notify the Company in writing of
the Securities selected for redemption as aforesaid and, in case of any
Securities selected for partial redemption as aforesaid, the principal amount
thereof to be redeemed.

                  The provisions of the two preceding paragraphs shall not apply
with respect to any redemption affecting only a single Security, whether such
Security is to be redeemed in whole or in part. In the case of any such
redemption in part, the unredeemed portion of the principal amount of the
Security shall be in an authorized denomination (which shall not be less than
the minimum authorized denomination) for such Security.

                  For all purposes of this Indenture, unless the context
otherwise requires, all provisions relating to the redemption of Securities
shall relate, in the case of any Securities redeemed or to be redeemed only in
part, to the portion of the principal amount of such Securities which has been
or is to be redeemed.


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<PAGE>   72


SECTION 11.4   NOTICE OF REDEMPTION.

                  Notice of redemption shall be given by first-class mail,
postage prepaid, mailed not less than 30 nor more than 60 days prior to the
Redemption Date, unless a shorter period is specified in the Securities to be
redeemed, to each Holder of Securities to be redeemed, at its address appearing
in the Security Register.

                  All notices of redemption shall state:

                           (1) the Redemption Date,

                           (2) the Redemption Price (including accrued interest,
         if any),

                           (3) if less than all the Outstanding Securities of
         any series consisting of more than a single Security are to be
         redeemed, the identification (and, in the case of partial redemption of
         any such Securities, the principal amounts) of the particular
         Securities to be redeemed and, if less than all the Outstanding
         Securities of any series consisting of a single Security are to be
         redeemed, the principal amount of the particular Security to be
         redeemed,

                           (4) that on the Redemption Date the Redemption Price
         will become due and payable upon each such Security to be redeemed and,
         if applicable, that interest thereon will cease to accrue on and after
         said date,

                           (5) the place or places where each such Security is
         to be surrendered for payment of the Redemption Price,

                           (6) if applicable, the conversion price, the date on
         which the right to convert the principal of the Securities or the
         portions thereof to be redeemed will terminate, and the place or places
         where such Securities may be surrendered for conversion, and

                           (7) that the redemption is for a sinking fund, if
         such is the case.

                  Notice of redemption of Securities to be redeemed at the
election of the Company shall be given by the Company or, at the Company's
request, by the Trustee in the name and at the expense of the Company and shall
be irrevocable.


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<PAGE>   73


SECTION 11.5   DEPOSIT OF REDEMPTION PRICE.

                  On or prior to any Redemption Date, the Company shall deposit
with the Trustee or with a Paying Agent (or, if the Company is acting as its own
Paying Agent, segregate and hold in trust as provided in Section 10.3) an amount
of money sufficient to pay the Redemption Price of, and (except if the
Redemption Date shall be an Interest Payment Date) accrued interest on, all the
Securities which are to be redeemed on that date.

                  If any Security called for redemption is converted, any money
deposited with the Trustee or with a Paying Agent or so segregated and held in
trust for the redemption of such Security shall (subject to the right of any
Holder of such Security to receive interest as provided in the last paragraph of
Section 3.7) be paid to the Company on Company Request, or if then held by the
Company, shall be discharged from such trust.

SECTION 11.6 SECURITIES PAYABLE ON REDEMPTION DATE.

                  Notice of redemption having been given as aforesaid, the
Securities so to be redeemed shall, on the Redemption Date, become due and
payable at the Redemption Price therein specified, and from and after such date
(unless the Company shall default in the payment of the Redemption Price and
accrued interest) such Securities shall cease to bear interest. Upon surrender
of any such Security for redemption in accordance with said notice, such
Security shall be paid by the Company at the Redemption Price, together with
accrued interest to the Redemption Date; provided, however, that, unless
otherwise specified as contemplated by Section 3.1, installments of interest
whose Stated Maturity is on or prior to the Redemption Date will be payable to
the Holders of such Securities, or one or more Predecessor Securities,
registered as such at the close of business on the relevant Record Dates
according to their terms and the provisions of Section 3.7.

                  If any Security called for redemption shall not be so paid
upon surrender thereof for redemption, the principal and any premium shall,
until paid, bear interest from the Redemption Date at the rate prescribed
therefor in the Security.

SECTION 11.7 SECURITIES REDEEMED IN PART.

                  Any Security which is to be redeemed only in part shall be
surrendered at a Place of Payment therefor (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 its attorney duly authorized in writing), and the Company shall execute, and
the Trustee shall authenticate and deliver to the Holder of such Security
without service charge, a new Security or Securities of the


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<PAGE>   74


same series and of like tenor, of any authorized denomination as requested by
such Holder, in aggregate principal amount equal to and in exchange for the
unredeemed portion of the principal of the Security so surrendered.


                                   ARTICLE XII

                                  SINKING FUNDS

SECTION 12.1 APPLICABILITY OF ARTICLE.

                  The provisions of this Article shall be applicable to any
sinking fund for the retirement of Securities of any series except as otherwise
specified as contemplated by Section 3.1 for such Securities.

                  The minimum amount of any sinking fund payment provided for by
the terms of any Securities is herein referred to as a "mandatory sinking fund
payment," and any payment in excess of such minimum amount provided for by the
terms of such Securities is herein referred to as an "optional sinking fund
payment." If provided for by the terms of any Securities, the cash amount of any
sinking fund payment may be subject to reduction as provided in Section 12.2.
Each sinking fund payment shall be applied to the redemption of Securities as
provided for by the terms of such Securities.

SECTION 12.2 SATISFACTION OF SINKING FUND PAYMENTS WITH SECURITIES.

                  The Company (1) may deliver Outstanding Securities of a series
(other than any previously called for redemption) and (2) may apply as a credit
Securities of a series which have been redeemed either at the election of the
Company pursuant to the terms of such Securities or through the application of
permitted optional sinking fund payments pursuant to the terms of such
Securities, in each case in satisfaction of all or any part of any sinking fund
payment with respect to any Securities of such series required to be made
pursuant to the terms of such Securities as and to the extent provided for by
the terms of such Securities; provided that the Securities to be so credited
have not been previously so credited. The Securities to be so credited shall be
received and credited for such purpose by the Trustee at the Redemption Price,
as specified in the Securities so to be redeemed, for redemption through
operation of the sinking fund and the amount of such sinking fund payment shall
be reduced accordingly.


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<PAGE>   75


SECTION 12.3 REDEMPTION OF SECURITIES FOR SINKING FUND.

                  Not less than 60 days prior to each sinking fund payment date
for any Securities, the Company will deliver to the Trustee an Officers'
Certificate specifying the amount of the next ensuing sinking fund payment for
such Securities pursuant to the terms of such Securities, the portion thereof,
if any, which is to be satisfied by payment of cash and the portion thereof, if
any, which is to be satisfied by delivering and crediting Securities pursuant to
Section 12.2 and will also deliver to the Trustee any Securities to be so
delivered. Not less than 30 days prior to each such sinking fund payment date,
the Trustee shall select the Securities to be redeemed upon such sinking fund
payment date in the manner specified in Section 11.3 and cause notice of the
redemption thereof to be given in the name of and at the expense of the Company
in the manner provided in Section 11.4. Such notice having been duly given, the
redemption of such Securities shall be made upon the terms and in the manner
stated in Sections 11.6 and 11.7.

                                  ARTICLE XIII

                       DEFEASANCE AND COVENANT DEFEASANCE

SECTION 13.1 COMPANY'S OPTION TO EFFECT DEFEASANCE OR COVENANT DEFEASANCE.

                  The Company may elect, at its option at any time, to have
Section 13.2 or Section 13.3 applied to any Securities or any series of
Securities, as the case may be, designated pursuant to Section 3.1 as being
defeasible pursuant to such Section 13.2 or 13.3, in accordance with any
applicable requirements provided pursuant to Section 3.1 and upon compliance
with the conditions set forth below in this Article. Any such election shall be
evidenced by a Board Resolution or in another manner specified as contemplated
by Section 3.1 for such Securities.

SECTION 13.2 DEFEASANCE AND DISCHARGE.

                  Upon the Company's exercise of its option (if any) to have
this Section applied to any Securities or any series of Securities, as the case
may be, the Company shall be deemed to have been discharged from its
obligations, and the provisions of Article 15 shall cease to be effective, with
respect to such Securities as provided in this Section on and after the date the
conditions set forth in Section 13.4 are satisfied (hereinafter called
"Defeasance"). For this purpose, such Defeasance means that the Company shall be
deemed to have paid and discharged the entire indebtedness represented by such
Securities and to have satisfied all its other obligations under such Securities
and this Indenture insofar as such Securities are concerned (and the Trustee, at



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<PAGE>   76


the expense of the Company, shall execute proper instruments acknowledging the
same), subject to the following which shall survive until otherwise terminated
or discharged hereunder:

                           (1) the rights of Holders of such Securities to
         receive, solely from the trust fund described in Section 13.4 and as
         more fully set forth in such Section, payments in respect of the
         principal of and any premium and interest on such Securities when
         payments are due;

                           (2) the Company's obligations with respect to such
         Securities under Sections 3.4, 3.5, 3.6, 10.2 and 10.3, and, if
         applicable, Article 14;

                           (3) the rights, powers, trusts, duties and immunities
         of the Trustee hereunder; and

                           (4) this Article.

                  Subject to compliance with this Article, the Company may
exercise its option (if any) to have this Section applied to any Securities
notwithstanding the prior exercise of its option (if any) to have Section 13.3
applied to such Securities.

SECTION 13.3 COVENANT DEFEASANCE.

                  Upon the Company's exercise of its option (if any) to have
this Section applied to any Securities or any series of Securities, as the case
may be:

                           (1) the Company shall be released from its
         obligations under any covenants provided pursuant to Section 3.1(20) or
         9.1(2) or for the benefit of the Holders of such Securities;

                           (2) the occurrence of any event specified in any
         covenants provided pursuant to Section 3.1(20) or 9.1(2) shall be
         deemed not to be or result in an Event of Default; and

                           (3) the provisions of Article 15 shall cease to be
         effective,

in each case with respect to such Securities as provided in this Section on and
after the date the conditions set forth in Section 13.4 are satisfied
(hereinafter called "Covenant Defeasance"). For this purpose, such Covenant
Defeasance means that, with respect to such Securities, the Company may omit to
comply with and shall have no liability in respect of any term, condition or
limitation set forth in any such specified Section (to the extent so specified
in the case of Section 5.1(4)) or Article 15, whether directly or


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<PAGE>   77


indirectly by reason of any reference elsewhere herein to any such Section or by
reason of any reference in any such Section or Article to any other provision
herein or in any other document, but the remainder of this Indenture and such
Securities shall be unaffected thereby.

SECTION 13.4 CONDITIONS TO DEFEASANCE OR COVENANT DEFEASANCE.

                  The following shall be the conditions to the application of
Section 13.2 or Section 13.3 to any Securities or any series of Securities, as
the case may be:

                           (1) The Company shall irrevocably have deposited or
         caused to be deposited with the Trustee (or another trustee which
         satisfies the requirements contemplated by Section 6.9 and agrees to
         comply with the provisions of this Article applicable to it) as trust
         funds in trust for the purpose of making the following payments,
         specifically pledged as security for, and dedicated solely to, the
         benefits of the Holders of such Securities, (A) money in an amount, or
         (B) U.S. Government Obligations which through the scheduled payment of
         principal and interest in respect thereof in accordance with their
         terms will provide, not later than one day before the due date of any
         payment, money in an amount, or (C) a combination thereof, in each case
         sufficient, in the opinion of a nationally recognized firm of
         independent public accountants expressed in a written certification
         thereof delivered to the Trustee, to pay and discharge, and which shall
         be applied by the Trustee (or any such other qualifying trustee) to pay
         and discharge, the principal of and any premium and interest on such
         Securities on the respective Stated Maturities, in accordance with the
         terms of this Indenture and such Securities. As used herein, "U.S.
         Government Obligation" means (x) any security which is (i) a direct
         obligation of the United States of America for the payment of which the
         full faith and credit of the United States of America is pledged or
         (ii) an obligation of a Person controlled or supervised by and acting
         as an agency or instrumentality of the United States of America the
         payment of which is unconditionally guaranteed as a full faith and
         credit obligation by the United States of America, which, in either
         case (i) or (ii), is not callable or redeemable at the option of the
         issuer thereof, and (y) any depositary receipt issued by a bank (as
         defined in Section 3(a)(2) of the Securities Act) as custodian with
         respect to any U.S. Government Obligation which is specified in Clause
         (x) above and held by such bank for the account of the holder of such
         depositary receipt, or with respect to any specific payment of
         principal of or interest on any U.S. Government Obligation which is so
         specified and held, provided that (except as required by law)


                                       70
<PAGE>   78


         such custodian is not authorized to make any deduction from the amount
         payable to the holder of such depositary receipt from any amount
         received by the custodian in respect of the U.S. Government Obligation
         or the specific payment of principal or interest evidenced by such
         depositary receipt.

                           (2) In the event of an election to have Section 13.2
         apply to any Securities or any series of Securities, as the case may
         be, the Company shall have delivered to the Trustee an Opinion of
         Counsel stating that (A) the Company has received from, or there has
         been published by, the Internal Revenue Service a ruling or (B) since
         the date of this instrument, there has been a change in the applicable
         Federal income tax law, in either case (A) or (B) to the effect that,
         and based thereon such opinion shall confirm that, the Holders of such
         Securities will not recognize gain or loss for Federal income tax
         purposes as a result of the deposit, Defeasance and discharge to be
         effected with respect to such Securities and will be subject to Federal
         income tax on the same amount, in the same manner and at the same times
         as would be the case if such deposit, Defeasance and discharge were not
         to occur.

                           (3) In the event of an election to have Section 13.3
         apply to any Securities or any series of Securities, as the case may
         be, the Company shall have delivered to the Trustee an Opinion of
         Counsel to the effect that the Holders of such Securities will not
         recognize gain or loss for Federal income tax purposes as a result of
         the deposit and Covenant Defeasance to be effected with respect to such
         Securities and will be subject to Federal income tax on the same
         amount, in the same manner and at the same times as would be the case
         if such deposit and Covenant Defeasance were not to occur.

                           (4) The Company shall have delivered to the Trustee
         an Officers' Certificate to the effect that neither such Securities nor
         any other Securities of the same series, if then listed on any
         securities exchange, will be delisted as a result of such deposit.

                           (5) No event which is, or after notice or lapse of
         time or both would become, an Event of Default with respect to such
         Securities or any other Securities shall have occurred and be
         continuing at the time of such deposit or, with regard to any such
         event specified in Sections 5.1(5) and (6), at any time on or prior to
         the 90th day after the date of such deposit (it being understood that
         this condition shall not be deemed satisfied until after such 90th
         day).


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<PAGE>   79


                           (6) Such Defeasance or Covenant Defeasance shall not
         cause the Trustee to have a conflicting interest within the meaning of
         the Trust Indenture Act (assuming all Securities are in default within
         the meaning of such Act).

                           (7) Such Defeasance or Covenant Defeasance shall not
         result in a breach or violation of, or constitute a default under, any
         other agreement or instrument to which the Company is a party or by
         which it is bound.

                           (8) Such Defeasance or Covenant Defeasance shall not
         result in the trust arising from such deposit constituting an
         investment company within the meaning of the Investment Company Act
         unless such trust shall be registered under such Act or exempt from
         registration thereunder.

                           (9) At the time of such deposit,

                                    (A) no default in the payment of principal
                           of or any premium or interest on any Senior
                           Indebtedness shall have occurred and be continuing,

                                    (B) no event of default with respect to any
                           Senior Indebtedness shall have resulted in such
                           Senior Indebtedness becoming, and continuing to be,
                           due and payable prior to the date on which it would
                           otherwise have become due and payable (unless payment
                           of such Senior Indebtedness has been made or duly
                           provided for), and

                                    (C) no other event of default with respect
                           to any Senior Indebtedness shall have occurred and be
                           continuing permitting (after notice or lapse of time
                           or both) the holders of such Senior Indebtedness (or
                           a trustee on behalf of such holders) to declare such
                           Senior Indebtedness due and payable prior to the date
                           on which it would otherwise have become due and
                           payable.

                           (10) The Company shall have delivered to the Trustee
         an Officers' Certificate and an Opinion of Counsel, each stating that
         all conditions precedent with respect to such Defeasance or Covenant
         Defeasance have been complied with.


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<PAGE>   80


SECTION 13.5 DEPOSITED MONEY AND U.S. GOVERNMENT OBLIGATIONS
             TO BE HELD IN TRUST; MISCELLANEOUS PROVISIONS.

                  Subject to the provisions of the last paragraph of Section
10.3, all money and U.S. Government Obligations (including the proceeds thereof)
deposited with the Trustee or other qualifying trustee (solely for purposes of
this Section and Section 13.6, the Trustee and any such other trustee are
referred to collectively as the "Trustee") pursuant to Section 13.4 in respect
of any Securities shall be held in trust and applied by the Trustee, in
accordance with the provisions of such Securities and this Indenture, to the
payment, either directly or through any such Paying Agent (including the Company
acting as its own Paying Agent) as the Trustee may determine, to the Holders of
such Securities, of all sums due and to become due thereon in respect of
principal and any premium and interest, but money so held in trust need not be
segregated from other funds except to the extent required by law. Monies and
U.S. Government Obligations so held in trust shall not be subject to the
provisions of Article 15.

                  The Company shall pay and indemnify the Trustee against any
tax, fee or other charge imposed on or assessed against the U.S. Government
Obligations deposited pursuant to Section 13.4 or the principal and interest
received in respect thereof other than any such tax, fee or other charge which
by law is for the account of the Holders of Outstanding Securities.

                  Anything in this Article to the contrary notwithstanding, the
Trustee shall deliver or pay to the Company from time to time upon Company
Request any money or U.S. Government Obligations held by it as provided in
Section 13.4 with respect to any Securities which, in the opinion of a
nationally recognized firm of independent public accountants expressed in a
written certification thereof delivered to the Trustee, are in excess of the
amount thereof which would then be required to be deposited to effect the
Defeasance or Covenant Defeasance, as the case may be, with respect to such
Securities.

SECTION 13.6 REINSTATEMENT.

                  If the Trustee or the Paying Agent is unable to apply any
money in accordance with this Article with respect to any Securities by reason
of any order or judgment of any court or governmental authority enjoining,
restraining or otherwise prohibiting such application, then the obligations
under this Indenture and such Securities from which the Company has been
discharged or released pursuant to Section 13.2 or 13.3 shall be revived and
reinstated as though no deposit had occurred pursuant to this Article with
respect to such Securities, until such time as the Trustee or Paying Agent is
permitted to apply all money held in trust pursuant to Section 13.5 with respect
to such Securities in accordance with this Article; provided, however, that if
the Company makes


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<PAGE>   81


any payment of principal of or any premium or interest on any such Security
following such reinstatement of its obligations, the Company shall be subrogated
to the rights (if any) of the Holders of such Securities to receive such payment
from the money so held in trust.


                                   ARTICLE XIV

                            CONVERSION OF SECURITIES

SECTION 14.1 APPLICABILITY OF ARTICLE.

                  The provisions of this Article shall be applicable to the
Securities of any series which are convertible into shares of Common Stock of
the Company, and the issuance of such shares of Common Stock upon the conversion
of such Securities, except as otherwise specified as contemplated by Section 3.1
for the Securities of such series.

SECTION 14.2 EXERCISE OF CONVERSION PRIVILEGE.

                  In order to exercise a conversion privilege, the Holder of a
Security of a series with such a privilege shall surrender such Security to the
Company at the office or agency maintained for that purpose pursuant to Section
10.2, accompanied by a duly executed conversion notice to the Company
substantially in the form set forth in Section 2.6 stating that the Holder
elects to convert such Security or a specified portion thereof. Such notice
shall also state, if different from the name and address of such Holder, the
name or names (with address) in which the certificate or certificates for shares
of Common Stock which shall be issuable on such conversion shall be issued.
Securities surrendered for conversion shall (if so required by the Company or
the Trustee) be duly endorsed by or accompanied by instruments of transfer in
forms satisfactory to the Company and the Trustee duly executed by the
registered Holder or its attorney duly authorized in writing; and Securities so
surrendered for conversion (in whole or in part) during the period from the
close of business on any Regular Record Date to the opening of business on the
next succeeding Interest Payment Date (excluding Securities or portions thereof
called for redemption during the period beginning at the close of business on a
Regular Record Date and ending at the opening of business on the first Business
Day after the next succeeding Interest Payment Date, or if such Interest Payment
Date is not a Business Day, the second such Business Day) shall also be
accompanied by payment in funds acceptable to the Company of an amount equal to
the interest payable on such Interest Payment Date on the principal amount of
such Security then being converted, and such interest shall be payable to such
registered Holder notwithstanding the conversion of such Security, subject to
the provisions of Section 3.7 relating to the payment of Defaulted Interest by
the Company. As promptly as practicable after the receipt of such notice and of
any payment required pursuant to a Board Resolution and, subject to



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<PAGE>   82


Section 3.3, set forth, or determined in the manner provided, in an Officers'
Certificate, or established in one or more indentures supplemental hereto
setting forth the terms of such series of Security, and the surrender of such
Security in accordance with such reasonable regulations as the Company may
prescribe, the Company shall issue and shall deliver, at the office or agency at
which such Security is surrendered, to such Holder or on its written order, a
certificate or certificates for the number of full shares of Common Stock
issuable upon the conversion of such Security (or specified portion thereof), in
accordance with the provisions of such Board Resolution, Officers' Certificate
or supplemental indenture, and cash as provided therein in respect of any
fractional share of such Common Stock otherwise issuable upon such conversion.
Such conversion shall be deemed to have been effected immediately prior to the
close of business on the date on which such notice and such payment, if
required, shall have been received in proper order for conversion by the Company
and such Security shall have been surrendered as aforesaid (unless such Holder
shall have so surrendered such Security and shall have instructed the Company to
effect the conversion on a particular date following such surrender and such
Holder shall be entitled to convert such Security on such date, in which case
such conversion shall be deemed to be effected immediately prior to the close of
business on such date) and at such time the rights of the Holder of such
Security as such Security Holder shall cease and the person or persons in whose
name or names any certificate or certificates for shares of Common Stock of the
Company shall be issuable upon such conversion shall be deemed to have become
the Holder or Holders of record of the shares represented thereby. Except as set
forth above and subject to the final paragraph of Section 3.7, no payment or
adjustment shall be made upon any conversion on account of any interest accrued
on the Securities (or any part thereof) surrendered for conversion or on account
of any dividends on the Common Stock of the Company issued upon such conversion.
In the case of any Security which is converted in part only, upon such
conversion the Company shall execute and the Trustee shall authenticate and
deliver to or on the order of the Holder thereof, at the expense of the Company,
a new Security or Securities of the same series, of authorized denominations, in
aggregate principal amount equal to the unconverted portion of such Security.

SECTION 14.3 NO FRACTIONAL SHARES.

                  No fractional share of Common Stock of the Company shall be
issued upon conversions of Securities of any series. If more than one Security
shall be surrendered for conversion at one time by the same Holder, the number
of full shares which shall be issuable upon conversion shall be computed on the
basis of the aggregate principal amount of the Securities (or specified portions
thereof to the extent permitted hereby) so surrendered. If, except for the
provisions of this Section 14.3, any Holder of a Security or Securities would be
entitled to a fractional share of Common Stock of the Company upon the
conversion of such Security or Securities, or specified portions thereof, the
Company shall pay to such Holder an amount in cash equal to the current

                                       75
<PAGE>   83


market value of such fractional share computed, (i) if such Common Stock is
listed or admitted to unlisted trading privileges on a national securities
exchange or market, on the basis of the last reported sale price on such
exchange or market on the last trading day prior to the date of conversion upon
which such a sale shall have been effected, or (ii) if such Common Stock is not
at the time so listed or admitted to unlisted trading privileges on a national
securities exchange or market, on the basis of the average of the bid and asked
prices of such Common Stock in the over-the-counter market, on the last trading
day prior to the date of conversion, as reported by the National Quotation
Bureau, Incorporated or similar organization if the National Quotation Bureau,
Incorporated is no longer reporting such information, or if not so available,
the fair market price as determined by the Board of Directors. For purposes of
this Section, "trading day" shall mean each Monday, Tuesday, Wednesday, Thursday
and Friday other than any day on which the Common Stock is not traded on the New
York Stock Exchange, or if the Common Stock is not traded on the New York Stock
Exchange, on the principal exchange or market on which the Common Stock is
traded or quoted.

SECTION 14.4 ADJUSTMENT OF CONVERSION PRICE.

                  The conversion price of Securities of any series that is
convertible into Common Stock of the Company shall be adjusted for any stock
dividends, stock splits, reclassifications, combinations or similar transactions
in accordance with the terms of the supplemental indenture or Board Resolutions
setting forth the terms of the Securities of such series. Whenever the
conversion price is adjusted, the Company shall compute the adjusted conversion
price in accordance with terms of the applicable Board Resolution or
supplemental indenture and shall prepare an Officers' Certificate setting forth
the adjusted conversion price and showing in reasonable detail the facts upon
which such adjustment is based, and such certificate shall forthwith be filed at
each office or agency maintained for the purpose of conversion of Securities
pursuant to Section 10.2 and, if different, with the Trustee. The Company shall
forthwith cause a notice setting forth the adjusted conversion price to be
mailed, first class postage prepaid, to each Holder of Securities of such series
at its address appearing on the Security Register and to any conversion agent
other than the Trustee.

SECTION 14.5 NOTICE OF CERTAIN CORPORATE ACTIONS.

                  In case:

                           (1) the Company shall declare a dividend (or any
         other distribution) on its Common Stock payable otherwise than in cash
         out of its retained earnings (other than a dividend for which approval
         of any shareholders of the Company is required) that would require an
         adjustment pursuant to Section 14.4; or


                                       76
<PAGE>   84


                           (2) the Company shall authorize the granting to all
         or substantially all of the holders of its Common Stock of rights,
         options or warrants to subscribe for or purchase any shares of capital
         stock of any class or of any other rights (other than any such grant
         for which approval of any shareholders of the Company is required); or

                           (3) of any reclassification of the Common Stock of
         the Company (other than a subdivision or combination of its outstanding
         shares of Common Stock, or of any consolidation, merger or share
         exchange to which the Company is a party and for which approval of any
         shareholders of the Company is required), or of the sale of all or
         substantially all of the assets of the Company; or

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

then the Company shall cause to be filed with the Trustee, and shall cause to be
mailed to all Holders at their last addresses as they shall appear in the
Security Register, at least 20 days (or 10 days in any case specified in Clause
(1) or (2) above) prior to the applicable record date hereinafter specified, a
notice stating (i) the date on which a record is to be taken for the purpose of
such dividend, distribution, rights, options or warrants, or, if a record is not
to be taken, the date as of which the holders of Common Stock of Record to be
entitled to such dividend, distribution, rights, options or warrants are to be
determined, or (ii) the date on which such reclassification, consolidation,
merger, share exchange, sale, dissolution, liquidation or winding up 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, cash or other property deliverable upon such
reclassification, consolidation, merger, share exchange, sale, dissolution,
liquidation or winding up. If at any time the Trustee shall not be the
conversion agent, a copy of such notice shall also forthwith be filed by the
Company with the Trustee.

SECTION 14.6 RESERVATION OF SHARES OF COMMON STOCK.

                  The Company shall at all times reserve and keep available,
free from preemptive rights, out of its authorized but unissued Common Stock,
for the purpose of effecting the conversion of Securities, the full number of
shares of Common Stock of the Company then issuable upon the conversion of all
outstanding Securities of any series that has conversion rights.


                                       77
<PAGE>   85


SECTION 14.7 PAYMENT OF CERTAIN TAXES UPON CONVERSION.

                  Except as provided in the next sentence, the Company will pay
any and all taxes that may be payable in respect of the issue or delivery of
shares of its 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 and delivery of shares of its
Common Stock in a name other than that of the Holder of the Security or
Securities to be converted, 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
any such tax, or has established, to the satisfaction of the Company, that such
tax has been paid.

SECTION 14.8 NONASSESSABILITY.

                  The Company covenants that all shares of its Common Stock
which may be issued upon conversion of Securities will upon issue in accordance
with the terms hereof be duly and validly issued and fully paid and
nonassessable.

SECTION 14.9 PROVISION IN CASE OF CONSOLIDATION, MERGER OR SALE OF ASSETS.

                  In case of any consolidation or merger of the Company with or
into any other Person, any merger of another Person with or into the Company
(other than a merger which does not result in any reclassification, conversion,
exchange or cancellation of outstanding shares of Common Stock of the Company)
or any conveyance, sale, transfer or lease of all or substantially all of the
assets of the Company, the Person formed by such consolidation or resulting from
such merger or which acquires such assets, as the case may be, shall execute and
deliver to the Trustee a supplemental indenture providing that the Holder of
each Security of a series then Outstanding that is convertible into Common Stock
of the Company shall have the right thereafter (which right shall be the
exclusive conversion right thereafter available to said Holder), during the
period such Security shall be convertible, to convert such Security only into
the kind and amount of securities, cash and other property receivable upon such
consolidation, merger, conveyance, sale, transfer or lease by a holder of the
number of shares of Common Stock of the Company into which such Security might
have been converted immediately prior to such consolidation, merger, conveyance,
sale, transfer or lease, assuming such holder of Common Stock of the Company (i)
is not a Person with which the Company consolidated or merged with or into or
which merged into or with the Company or to which such conveyance, sale,
transfer or lease was made, as the case may be (a "Constituent Person"), or an
Affiliate of a Constituent Person and (ii) failed to exercise his rights of
election, if any, as to the kind or amount of securities, cash and other
property receivable upon such consolidation, merger, conveyance, sale, transfer
or lease (provided that if the kind or


                                       78
<PAGE>   86


amount of securities, cash and other property receivable upon such
consolidation, merger, conveyance, sale, transfer, or lease is not the same for
each share of Common Stock of the Company held immediately prior to such
consolidation, merger, conveyance, sale, transfer or lease by others than a
Constituent Person or an Affiliate thereof and in respect of which such rights
of election shall not have been exercised ("Non-electing Share"), then for the
purpose of this Section 14.9 the kind and amount of securities, cash and other
property receivable upon such consolidation, merger, conveyance, sale, transfer
or lease by the holders of 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, for
events subsequent to the effective date of such supplemental indenture, shall be
as nearly equivalent as may be practicable to the adjustments provided for in
this Article or in accordance with the terms of the supplemental indenture or
Board Resolutions setting forth the terms of such adjustments. The above
provisions of this Section 14.9 shall similarly apply to successive
consolidations, mergers, conveyances, sales, transfers or leases. Notice of the
execution of such a supplemental indenture shall be given by the Company to the
Holder of each Security of a series that is convertible into Common Stock of the
Company as provided in Section 1.6 promptly upon such execution. Neither the
Trustee nor any conversion agent, if any, shall be under any responsibility to
determine the correctness of any provisions contained in any such supplemental
indenture relating either to the kind or amount of shares of stock or other
securities or property or cash receivable by Holders of Securities of a series
convertible into Common Stock of the Company upon the conversion of their
Securities after any such consolidation, merger, conveyance, transfer, sale or
lease or to any such adjustment, but may accept as conclusive evidence of the
correctness of any such provisions, and shall be protected in relying upon, an
Opinion of Counsel with respect thereto, which the Company shall cause to be
furnished to the Trustee upon request.

SECTION 14.10 DUTIES OF TRUSTEE REGARDING CONVERSION.

                  Neither the Trustee nor any conversion agent shall at any time
be under any duty or responsibility to any Holder of Securities of any series
that is convertible into Common Stock of the Company to determine whether any
facts exist which may require any adjustment of the conversion price, or with
respect to the nature or extent of any such adjustment when made, or with
respect to the method employed, whether herein or in any supplemental indenture,
any resolutions of the Board of Directors or written instrument executed by one
or more officers of the Company provided to be employed in making the same.
Neither the Trustee nor any conversion agent shall be accountable with respect
to the validity or value (or the kind or amount) of any shares of Common Stock
of the Company, or of any securities or property, which may at any time be
issued or delivered upon the conversion of any Securities and neither the
Trustee nor any conversion agent makes any representation with respect thereto.
Subject to the provisions of Section 6.1,


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<PAGE>   87


neither the Trustee nor any conversion agent shall be responsible for any
failure of the Company to issue, transfer or deliver any shares of its Common
Stock or stock certificates or other securities or property upon the surrender
of any Security for the purpose of conversion or to comply with any of the
covenants of the Company contained in this Article 14 or in the applicable
supplemental indenture, resolutions of the Board of Directors or written
instrument executed by one or more duly authorized officers of the Company.

SECTION 14.11 REPAYMENT OF CERTAIN FUNDS UPON CONVERSION.

                  Any funds which at any time shall have been deposited by the
Company or on its behalf with the Trustee or any other paying agent for the
purpose of paying the principal of and any premium and interest on any of the
Securities (including, but not limited to, funds deposited for the sinking fund
referred to in Article 12 hereof and funds deposited pursuant to Article 13
hereof) and which shall not be required for such purposes because of the
conversion of such Securities as provided in this Article 14 shall after such
conversion be repaid to the Company by the Trustee upon the Company's written
request.


                                   ARTICLE XV

                           SUBORDINATION OF SECURITIES

SECTION 15.1 AGREEMENT OF SUBORDINATION.

                  Except as otherwise provided in a supplemental indenture or
pursuant to Section 3.1, the Company covenants and agrees, and each Holder of
Securities issued hereunder by his acceptance thereof likewise covenants and
agrees, that all Securities shall be issued subject to the provisions of this
Article 15; and each Person holding any Security, whether upon original issue or
upon transfer, assignment or exchange thereof, accepts and agrees to be bound by
such provisions.

                  The payment of the principal of and any premium and interest
on all Securities (including, but not limited to, the redemption price with
respect to the Securities called for redemption in accordance with Article 11)
issued hereunder shall, to the extent and in the manner hereinafter set forth,
be subordinated and subject in right of payment to the prior payment in full of
all Senior Indebtedness, whether outstanding at the date of this Indenture or
thereafter incurred.

                  No provision of this Article 15 shall prevent the occurrence
of any default or Event of Default hereunder.


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<PAGE>   88


SECTION 15.2 PAYMENTS TO HOLDERS.

                  No payment shall be made with respect to the principal of or
any premium or interest on the Securities (including, but not limited to, the
redemption price with respect to the Securities to be called for redemption in
accordance with Article 11), except payments and distributions made by the
Trustee as permitted by the first or second paragraph of Section 15.5, if:

                  (i) a default in the payment of principal, premium, interest,
         rent or other obligations due on any Senior Indebtedness occurs and is
         continuing (or, in the case of Senior Indebtedness for which there is a
         period of grace, in the event of such a default that continues beyond
         the period of grace, if any, specified in the instrument or lease
         evidencing such Senior Indebtedness), unless and until such default
         shall have been cured or waived or shall have ceased to exist; or


                  (ii) a default, other than a payment default, on a Designated
         Senior Indebtedness occurs and is continuing that then permits holders
         of such Designated Senior Indebtedness to accelerate its maturity and
         the Trustee receives a notice of the default (a "Payment Blockage
         Notice") from a Representative or the Company.

                  If the Trustee receives any Payment Blockage Notice pursuant
to clause (ii) above, no subsequent Payment Blockage Notice shall be effective
for purposes of this Section unless and until (A) at least 365 days shall have
elapsed since the initial effectiveness of the immediately prior Payment
Blockage Notice, and (B) all scheduled payments of principal, premium, if any,
and interest on the Securities that have come due have been paid in full in
cash. No nonpayment default that existed or was continuing on the date of
delivery of any Payment Blockage Notice to the Trustee shall be, or be made, the
basis for a subsequent Payment Blockage Notice.

                  The Company may and shall resume payments on and distributions
in respect of the Securities upon the earlier of:

                  (1) the date upon which the default is cured or waived or
ceases to exist; or


                                       81
<PAGE>   89

                  (2) in the case of a default referred to in clause (ii) above,
179 days pass after notice is received if the maturity of such Designated Senior
Indebtedness has not been accelerated,

unless this Article 15 otherwise prohibits the payment or distribution at the
time of such payment or distribution.

                  Upon any payment by the Company, or distribution of assets of
the Company of any kind or character, whether in cash, property or securities,
to creditors upon any dissolution or winding-up or liquidation or reorganization
of the Company, whether voluntary or involuntary or in bankruptcy, insolvency,
receivership or other proceedings, all amounts due or to become due upon all
Senior Indebtedness shall first be paid in full in cash or other payment
satisfactory to the holders of such Senior Indebtedness, or payment thereof in
accordance with its terms provided for in cash or other payment satisfactory to
the holders of such Senior Indebtedness, before any payment is made on account
of the principal of or any premium or interest on the Securities (except
payments made pursuant to Article 4 from monies deposited with the Trustee
pursuant thereto prior to commencement of proceedings for such dissolution,
winding-up, liquidation or reorganization); and upon any such dissolution or
winding-up or liquidation or reorganization of the Company or bankruptcy,
insolvency, receivership or other proceeding, any payment by the Company, or
distribution of assets of the Company of any kind or character, whether in cash,
property or securities, to which the Holders of the Securities or the Trustee
would be entitled, except for the provision of this Article 15, shall (except as
aforesaid) be paid by the Company or by any receiver, trustee in bankruptcy,
liquidating trustee, agent or other Person making such payment or distribution,
or by the Holders of the Securities or by the Trustee under this Indenture if
received by them or it, directly to the holders of Senior Indebtedness (pro rata
to such holders on the basis of the respective amounts of Senior Indebtedness
held by such holders, or as otherwise required by law or a court order) or their
representative or representatives, or to the trustee or trustees under any
indenture pursuant to which any instruments evidencing any Senior Indebtedness
may have been issued, as their respective interests may appear, to the extent
necessary to pay all Senior Indebtedness in full, in cash or other payment
satisfactory to the holders of such Senior Indebtedness, after giving effect to
any concurrent payment or distribution to or for the holders of Senior
Indebtedness, before any payment or distribution or provision therefor is made
to the Holders of the Securities or to the Trustee.

                  For purposes of this Article 15, the words, "cash, property or
securities" shall not be deemed to include shares of stock of the Company as
reorganized or readjusted, or securities of the Company or any other corporation
provided for by a plan of reorganization or readjustment, the payment of which
is subordinated at least to the extent provided in this Article 15 with respect
to the Securities to the payment of all

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<PAGE>   90


Senior Indebtedness which may at the time be outstanding; provided that (i) the
Senior Indebtedness is assumed by the new corporation, if any, resulting from
any reorganization or readjustment and (ii) the rights of the holders of Senior
Indebtedness (other than leases which are not assumed by the Company or the new
corporation, as the case may be) are not, without the consent of such holders,
altered by such reorganization or readjustment. The consolidation of the Company
with, or the merger of the Company into, another corporation or the liquidation
or dissolution of the Company following the conveyance or transfer of its
property as an entirety, or substantially as an entirety, to another corporation
upon the terms and conditions provided for in Article 8 shall not be deemed a
dissolution, winding-up, liquidation or reorganization for the purposes of this
Section 15.2 if such other corporation shall, as a part of such consolidation,
merger, conveyance or transfer, comply with the conditions set forth in Article
8.

                  In the event of the acceleration of the Securities because of
an Event of Default, no payment or distribution shall be made to the Trustee or
any Holder of Securities in respect of the principal of or any premium or
interest on the Securities (including, but not limited to, the redemption price
with respect to the Securities called for redemption in accordance with Article
11), except payments and distributions made by the Trustee as permitted by the
first or second paragraph of Section 15.5, until all Senior Indebtedness has
been paid in full in cash or other payment satisfactory to the holders of Senior
Indebtedness or such acceleration is rescinded in accordance with the terms of
this Indenture. If payment of the Securities is accelerated because of an Event
of Default, the Company shall promptly notify holders of Senior Indebtedness of
the acceleration , unless there are no payment obligations of the Company
thereunder and all obligations thereunder to extend credit have been terminated
or expired.

                  In the event that, notwithstanding the foregoing provisions,
any payment or distribution of assets of the Company of any kind or character,
whether in cash, property or securities (including, without limitation, by way
of setoff or otherwise), prohibited by the foregoing, shall be received by the
Trustee or the Holders of the Securities before all Senior Indebtedness is paid
in full in cash or other payment satisfactory to the holders of such Senior
Indebtedness, or provision is made for such payment thereof in accordance with
its terms in cash or other payment satisfactory to the holders of such Senior
Indebtedness, such payment or distribution shall be held in trust for the
benefit of and shall be paid over or delivered to the holders of Senior
Indebtedness or their representative or representatives, or to the trustee or
trustees under any indenture pursuant to which any instruments evidencing any
Senior Indebtedness may have been issued, as their respective interests may
appear, as calculated by the Company, for application to the payment of all
Senior Indebtedness remaining unpaid to the extent necessary to pay all Senior
Indebtedness in full in cash or other payment satisfactory to the holders of
such Senior Indebtedness, after giving effect to any concurrent payment or
distribution to or for the holders of such Senior Indebtedness.


                                       83
<PAGE>   91


                  Nothing in this Section 15.2 shall apply to claims of, or
payments to, the Trustee under or pursuant to Section 6.7. This Section 15.2
shall be subject to the further provisions of Section 15.5.

SECTION 15.3 SUBROGATION OF SECURITIES.

                  Subject to the payment in full of all Senior Indebtedness, the
rights of the Holders of the Securities shall be subrogated to the extent of the
payments or distributions made to the holders of such Senior Indebtedness
pursuant to the provisions of this Article 15 (equally and ratably with the
holders of all indebtedness of the Company which by its express terms is
subordinated to other indebtedness of the Company to substantially the same
extent as the Securities are subordinated and is entitled to like rights of
subrogation) to the rights of the holders of Senior Indebtedness to receive
payments or distributions of cash, property or securities of the Company
applicable to the Senior Indebtedness until the principal of and any premium and
interest on the Securities shall be paid in full; and, for the purposes of such
subrogation, no payments or distributions to the holders of the Senior
Indebtedness of any cash, property or securities to which the Holders of the
Securities or the Trustee would be entitled except for the provisions of this
Article 15, and no payment over pursuant to the provisions of this Article 15,
to or for the benefit of the holders of Senior Indebtedness by Holders of the
Securities or the Trustee, shall, as between the Company, its creditors other
than holders of Senior Indebtedness, and the Holders of the Securities, be
deemed to be a payment by the Company to or on account of the Senior
Indebtedness; and no payments or distributions of cash, property or securities
to or for the benefit of the Holders of the Securities pursuant to the
subrogation provisions of this Article 15, which would otherwise have been paid
to the holders of Senior Indebtedness shall be deemed to be a payment by the
Company to or for the account of the Securities. It is understood that the
provisions of this Article 15 are and are intended solely for the purposes of
defining the relative rights of the Holders of the Securities, on the one hand,
and the holders of the Senior Indebtedness, on the other hand.

                  Nothing contained in this Article 15 or elsewhere in this
Indenture or in the Securities is intended to or shall impair, as among the
Company, its creditors other than the holders of Senior Indebtedness, and the
Holders of the Securities, the obligation of the Company, which is absolute and
unconditional, to pay to the Holders of the Securities the principal of and any
premium and interest on the Securities as and when the same shall become due and
payable in accordance with their terms, or is intended to or shall affect the
relative rights of the Holders of the Securities and creditors of the Company
other than the holders of the Senior Indebtedness, nor shall anything herein or
therein prevent the Trustee or the Holder of any Security from exercising all
remedies otherwise permitted by applicable law upon default under this
Indenture, subject to the rights, if any, under this Article 15 of the holders
of Senior Indebtedness in respect of cash, property or securities of the Company
received upon the exercise of any such remedy.


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<PAGE>   92


                  Upon any payment or distribution of assets of the Company
referred to in this Article 15, the Trustee, subject to the provisions of
Section 6.1, and the Holders of the Securities shall be entitled to rely upon
any order or decree made by any court of competent jurisdiction in which such
bankruptcy, dissolution, winding-up, liquidation or reorganization proceedings
are pending, or a certificate of the receiver, trustee in bankruptcy,
liquidating trustee, agent or other person making such payment or distribution,
delivered to the Trustee or to the Holders of the Securities, for the purpose of
ascertaining the persons entitled to participate in such distribution, the
holders of the Senior Indebtedness and other indebtedness of the Company, the
amount thereof or payable thereon and all other facts pertinent thereto or to
this Article 15.

SECTION 15.4 AUTHORIZATION TO EFFECT SUBORDINATION.

                  Each Holder of a Security by the Holder's acceptance thereof
authorizes and directs the Trustee on the Holder's behalf to take such action as
may be necessary or appropriate to effectuate the subordination as provided in
this Article 15 and appoints the Trustee to act as the Holder's attorney-in-fact
for any and all such purposes. If the Trustee does not file a proper proof of
claim or proof of debt in the form required in any proceeding referred to in
Section 5.3 hereof at least 30 days before the expiration of the time to file
such claim, the holders of any Senior Indebtedness or their representatives are
hereby authorized to file an appropriate claim for and on behalf of the Holders
of the Securities.

SECTION 15.5 NOTICE TO TRUSTEE.

                  The Company shall give prompt written notice in the form of an
Officers' Certificate to a Responsible Officer of the Trustee and to any paying
agent of any fact known to the Company which would prohibit the making of any
payment of monies to or by the Trustee or any paying agent in respect of the
Securities pursuant to the provisions of this Article 15. Notwithstanding the
provisions of this Article 15 or any other provision of this Indenture, the
Trustee shall not be charged with knowledge of the existence of any facts which
would prohibit the making of any payment of monies to or by the Trustee in
respect of the Securities pursuant to the provisions of this Article 15, unless
and until a Responsible Officer of the Trustee shall have received written
notice thereof at the Corporate Trust Office from the Company (in the form of an
Officers' Certificate) or a Representative or a holder or holders of Senior
Indebtedness or from any trustee thereof; and before the receipt of any such
written notice, the Trustee, subject to the provisions of Section 6.1, shall be
entitled in all respects to assume that no such facts exist; provided that if on
a date not fewer than two Business Days prior to the date upon


                                       85
<PAGE>   93

which by the terms hereof any such monies may become payable for any purpose
(including, without limitation, the payment of the principal of or any premium
or interest on any Security) the Trustee shall not have received, with respect
to such monies, the notice provided for in this Section 15.5, then, anything
herein contained to the contrary notwithstanding, the Trustee shall have full
power and authority to receive such monies and to apply the same to the purpose
for which they were received, and shall not be affected by any notice to the
contrary which may be received by it on or after such prior date.

                  Notwithstanding anything in this Article 15 to the contrary,
nothing shall prevent any payment by the Trustee to the Holders of monies
deposited with it pursuant to Section 4.1, and any such payment shall not be
subject to the provisions of Section 15.1 or Section 15.2.

                  The Trustee, subject to the provisions of Section 6.1, shall
be entitled to rely on the delivery to it of a written notice by a
Representative or a person representing himself to be a holder of Senior
Indebtedness (or a trustee on behalf of such holder) to establish that such
notice has been given by a Representative or a holder of Senior Indebtedness or
a trustee on behalf of any such holder or holders. In the event that the Trustee
determines in good faith that further evidence is required with respect to the
right of any person as a holder of Senior Indebtedness to participate in any
payment or distribution pursuant to this Article 15, the Trustee may request
such person to furnish evidence to the reasonable satisfaction of the Trustee as
to the amount of Senior Indebtedness held by such person, the extent to which
such person is entitled to participate in such payment or distribution and any
other facts pertinent to the rights of such person under this Article 15, and if
such evidence is not furnished, the Trustee may defer any payment to such person
pending judicial determination as to the right of such person to receive such
payment.


SECTION 15.6 TRUSTEE'S RELATION TO SENIOR INDEBTEDNESS.

                  The Trustee in its individual capacity shall be entitled to
all the rights set forth in this Article 15 in respect of any Senior
Indebtedness at any time held by it, to the same extent as any other holder of
Senior Indebtedness, and nothing in Section 6.13 or elsewhere in this Indenture
shall deprive the Trustee of any of its rights as such holder.

                  With respect to the holders of Senior Indebtedness, the
Trustee undertakes to perform or to observe only such of its covenants and
obligations as are specifically set forth in this Article 15, and no implied
covenants or obligations with respect to the holders of Senior Indebtedness
shall be read into this Indenture against the Trustee. The Trustee shall not be
deemed to owe any fiduciary duty to the holders of Senior Indebtedness and,
subject to the provisions of Section 6.1, the Trustee shall not be liable


                                       86
<PAGE>   94


to any holder of Senior Indebtedness if it shall pay over or deliver to Holders
of Securities, the Company or any other person money or assets to which any
holder of Senior Indebtedness shall be entitled by virtue of this Article 15 or
otherwise.

SECTION 15.7 NO IMPAIRMENT OF SUBORDINATION.

                  No right of any present or future holder of any Senior
Indebtedness to enforce subordination as herein provided shall at any time in
any way be prejudiced or impaired by any act or failure to act on the part of
the Company or by any act or failure to act, in good faith, by any such holder,
or by any noncompliance by the Company with the terms, provisions and covenants
of this Indenture, regardless of any knowledge thereof which any such holder may
have or otherwise be charged with.

SECTION 15.8 CERTAIN CONVERSIONS DEEMED PAYMENT.

                  For the purposes of this Article 15 only, (1) the issuance and
delivery of junior securities upon conversion of Securities in accordance with
Article 14 shall not be deemed to constitute a payment or distribution on
account of the principal of or any premium or interest on Securities or on
account of the purchase or other acquisition of Securities and (2) the payment,
issuance or delivery of cash (except in satisfaction of fractional shares
pursuant to Section 14.3), property or securities (other than junior securities)
upon conversion of a Security shall be deemed to constitute payment on account
of the principal of such Security. For the purposes of this Section 15.8, the
term "junior securities" means (a) shares of any stock of any class of the
Company or (b) securities of the Company which are subordinated in right of
payment to all Senior Indebtedness which may be outstanding at the time of
issuance or delivery of such securities to substantially the same extent as, or
to a greater extent than, the Securities are so subordinated as provided in this
Article. Nothing contained in this Article 15 or elsewhere in this Indenture or
in the Securities is intended to or shall impair, as among the Company, its
creditors (other than holders of Senior Indebtedness) and the Holders of
Securities, the right, which is absolute and unconditional, of the Holder of any
Security to convert such Security in accordance with Article 14.

SECTION 15.9 ARTICLE APPLICABLE TO PAYING AGENTS.

                  If at any time any Paying Agent (other than the Trustee) shall
have been appointed by the Company and be then acting hereunder, the term
"Trustee" as used in this Article shall (unless the context otherwise requires)
be construed as extending to and including such Paying Agent within its meaning
as fully for all intents and purposes as if such Paying Agent were named in this
Article in addition to or in place of the Trustee; provided, however, that the
first paragraph of Section 15.5 shall not apply to the Company or any Affiliate
of the Company if it or such Affiliate acts as Paying Agent.


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<PAGE>   95


SECTION 15.10 SENIOR INDEBTEDNESS ENTITLED TO RELY.

                  The holders of Senior Indebtedness (including, without
limitation, Designated Senior Indebtedness) shall have the right to rely upon
this Article 15, and no amendment or modification of the provisions contained
herein shall diminish the rights of such holders unless such holders shall have
agreed in writing thereto.

                  IN WITNESS WHEREOF, the parties hereto have caused this
Indenture to be duly executed as of the day and year first above written.

                                        WILLBROS GROUP, INC.


                                        By:
                                            ------------------------------
                                            Name:
                                            Title:


                                        ATTEST:

                                        [                     ],
                                         ---------------------
                                              as Trustee

                                        By:
                                            ------------------------------
                                             Name:
                                             Title:



                                       88