Document:

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                                  EXHIBIT 4.3
                                  -----------
                                AMENDMENT NO. 2

                                      TO

                                RADIO ONE, INC.
               1999 STOCK OPTION AND RESTRICTED STOCK GRANT PLAN

     The 1999 Stock Option and Restricted Stock Grant Plan (the "Plan") is
hereby amended as follows:

     1.  Article II (Definitions) is hereby amended by inserting the following
definition immediately before the definition of "Common Stock":  "`Class D
                                                 ------------      -------
Common Stock' means Class D Common Stock, $0.001 par value per share, of the
-------------
Company."

     2.  Article II (Definitions) is hereby amended by restating the definition
of "Common Stock" as follows:  "`Common Stock' means Class A Common Stock and
    ------------                 -------------
Class D Common Stock."

     3.  Article II (Definitions) is hereby amended by restating the definition
of "Fair Market Value" as follows:
    -----------------

      "Fair Market Value" per share on any given date means the average for the
        -----------------
      ten (10) preceding trading days of the closing prices of the sales of the
      relevant class of Common Stock (i.e., Class A Common Stock or Class D
      Common Stock) on all securities exchanges on which such stock may at the
      time be listed, or, if there have been no sales on any such exchange on
      any day, the average of the highest bid and lowest asked prices on all
      such exchanges at the end of such day for the relevant class of Common
      Stock, or, if on any day such stock is not so listed, the average of the
      representative bid and asked prices quoted on the Nasdaq Stock Market as
      of 4:00 p.m., New York time for the relevant class of Common Stock, or, if
      on any day such stock is not quoted on the Nasdaq Stock Market, the
      average of the highest bid and lowest asked prices on such day in the
      domestic over-the-counter market as reported by the National Quotation
      Bureau, Incorporated, or any similar successor organization for the
      relevant class of Common Stock.  If at any time any class of Common Stock
      is not listed or quoted, the Fair Market Value per share shall be
      determined by the Committee or the Board based on such factors as the
      members thereof in the exercise of their business judgment consider
      reasonably relevant.
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     4.  The first sentence of Article IV (Limitation on Aggregate Shares) is
amended to read as follows:

           The number of shares of Common Stock with respect to which Options
      and Grants may be granted under the Plan shall not exceed, in the
      aggregate, 1,408,099 shares of Class A Common Stock and 2,816,198 shares
      of Class D Common Stock, subject to adjustment in accordance with Section
      6.4.

      5. Article V (Awards) is amended by restating Section 5.1(c) as follows:

           (c) Exercise Price.  The exercise price per share of Common Stock
               --------------
      under each Option shall be determined by the Committee at the time of
      grant; provided, however, that the exercise price per share of Common
      Stock under each incentive stock option shall be fixed by the Committee at
      the time of grant of the Option and shall equal at least 100% of the Fair
      Market Value of a share of the relevant class of Common Stock on the date
      of grant, but not less than the par value per share (as adjusted pursuant
      to Section 6.4).  Subject to Section 5.7, Options shall be exercisable at
      such time or times as the Committee shall determine; provided, however,
      that any option intended to be an incentive stock option shall be treated
      as an incentive stock option only to the extent that the aggregate Fair
      Market Value of the relevant class of Common Stock (determined as of the
      date of Option grant) with respect to which incentive stock options (but
      not nonqualified options) are exercisable for the first time by any
      Participant during any calendar year (under all stock option plans of the
      Company and its Subsidiaries) does not exceed $100,000.

     6.  Article V (Awards) is amended by restating Section 5.1(d) as follows:

           (d) Option or Grant Term.  The Committee shall determine the term of
               --------------------
      each Option and Grant, which term shall not exceed ten years from the date
      of grant of the Grant or Option (five years in the case of incentive stock
      options for which the exercise price is 110% of the Fair Market Value of a
      share of the relevant class of Common Stock on the date of grant, pursuant
      to Section 5.1(b)).

     7.  Article V (Awards) is amended by restating Section 5.1(e) as follows:

           (e) Maximum Annual Grant to Participant.  In any one calendar year,
               -----------------------------------
      the Committee shall not grant to any one Participant Options to purchase,
      or Grants of, a number of shares of Class A Common Stock in excess of
      704,050 or a number of shares of Class D Common Stock in excess of
      1,408,099.

                                      -2-
<PAGE>

     8.  Article V (Awards) is amended by restating Section 5.3 as follows:

           5.3  Payment Options.  Options may be exercised, in whole or in part,
                ---------------
      upon payment of the exercise price of the Option Shares to be acquired.
      Payment shall be made:  (i) in cash (including check, bank draft or money
      order); (ii) by delivery of outstanding shares of Common Stock, of the
      same class for which the Option is to be exercised, with a Fair Market
      Value on the date of exercise equal to the aggregate exercise price
      payable with respect to the Options' exercise; (iii) by simultaneous sale
      through a broker reasonably acceptable to the Committee of Option Shares
      acquired on exercise, as permitted under Regulation T of the Federal
      Reserve Board or other method of legally permissible cashless exercise;
      (iv) by authorizing the Company to withhold from issuance a number of
      Option Shares issuable upon exercise of the Options which, when multiplied
      by the Fair Market Value of a share of the relevant class of Common Stock
      on the date of exercise is equal to the aggregate exercise price payable
      with respect to the Options so exercised; (v) by any combination of the
      foregoing; or (vi) in any additional manner the Committee approves.
      Options may also be exercised upon payment of the exercise price of the
      Option Shares to be acquired by delivery of the Participant's promissory
      note, but only to the extent specifically approved by and in accordance
      with the policies of the Committee.

                (a) Exchange of Previously Acquired Stock. In the event a
                    -------------------------------------
      Participant elects to pay the exercise price payable with respect to an
      Option pursuant to clause (ii) above, (A) only a whole number of share(s)
      of the relevant class of Common Stock (and not fractional shares of Common
      Stock) may be tendered in payment, (B) such Participant must present
      evidence acceptable to the Company that he or she has owned any such
      shares of the relevant class of Common Stock tendered in payment of the
      exercise price (and that such tendered shares of Common Stock have not
      been subject to any substantial risk of forfeiture) for at least six
      months prior to the date of exercise, and (C) the relevant class of Common
      Stock must be delivered to the Company. Delivery for this purpose may, at
      the election of the Participant, be made either by (A) physical delivery
      of the certificate(s) for all such shares of the relevant class of Common
      Stock tendered in payment of the price, accompanied by duly executed
      instruments of transfer in a form acceptable to the Company, or (B)
      direction to the Participant's broker to transfer, by book entry, such
      shares of the relevant class of Common Stock from a brokerage account of
      the Participant to a brokerage account specified by the Company. When
      payment of the exercise price is made by delivery of shares of the
      relevant class of Common Stock, the difference, if any, between the
      aggregate exercise price payable with respect to the Option being
      exercised and the Fair Market Value of the share(s) of the relevant class
      of Common Stock tendered in payment (plus any applicable taxes) shall be
      paid in cash. No Participant may tender shares of Common Stock having a
      Fair Market Value exceeding the aggregate exercise price payable with
      respect to the Option being exercised (plus any applicable taxes).

                                      -3-
<PAGE>

                (b) Payment by Withholding Shares. In the event a Participant
                    -----------------------------
      elects to pay the exercise price payable with respect to an option
      pursuant to clause (iv) above, (A) only a whole number of Option Share(s)
      (and not fractional Option Shares) may be withheld in payment and (B) such
      Participant must present evidence acceptable to the Company that he or she
      has owned a number of shares of the relevant class of Common Stock at
      least equal to the number of Option Shares to be withheld in payment of
      the exercise price (and that such owned shares of Common Stock have not
      been subject to any substantial risk of forfeiture) for at least six
      months prior to the date of exercise. When payment of the exercise price
      is made by withholding of Option Shares, the difference, if any, between
      the aggregate exercise price payable with respect to the option being
      exercised and the Fair Market Value of the Option Share(s) withheld in
      payment (plus any applicable taxes) shall be paid in cash. No Participant
      may authorize the withholding of Option Shares having a Fair Market Value
      exceeding the aggregate exercise price payable with respect to the Option
      being exercised (plus any applicable taxes). Any withheld Option Shares
      shall no longer be issuable under such Options.

     9.  Article V (Awards) is amended by restating Section 5.4 as follows:

           5.4  Grant of Reload Options.  The Committee may provide (either at
                -----------------------
      the time of grant or exercise of an Option), in its discretion, for the
      grant to a Participant who exercises all or any portion of an Option

      ("Exercised Options") and who pays all or part of such exercise price with
      -------------------
      shares of Common Stock, of an additional option (a "Reload Option") for a
                                                          -------------
      number of shares of Common Stock, of the same class as those shares used
      to pay all or part of the exercise price, equal to the sum (the "Reload
                                                                       ------
      Number") of the number of shares of Common Stock tendered or withheld in
      ------
      payment of such exercise price for the Exercised Options plus, if so
      provided by the Committee, the number of shares of Common Stock, if any,
      tendered or withheld by the Participant or withheld by the Company in
      connection with the exercise of the Exercised Options to satisfy any
      federal, state or local tax withholding requirements.  The terms of each
      Reload Option, including the date of its expiration and the terms and
      conditions of its exercisability and transferability, shall be the same as
      the terms of the Exercised Option to which it relates, except that:  (i)
      the grant date for each Reload Option shall be the date of exercise of the
      Exercised Option to which it relates and (ii) the exercise price for each
      Reload Option shall be the Fair Market Value of the Common Stock on the
      grant date of the Reload Option.

                                      -4-
<PAGE>

      10.  Article V (Awards) is amended by restating Section 5.5(a) as follows:

     5.5   Withholding Tax Requirements.
           ----------------------------

                (a) Participant Election.  Unless otherwise determined by the
                    --------------------
      Committee, a Participant may elect to deliver shares of the relevant class
      of Common Stock (or have the Company withhold shares acquired upon
      exercise of an Option or Grant) to satisfy, in whole or in part, the
      amount the Company is required to withhold for taxes in connection with
      the exercise of an option or a Grant.  Such election must be made on or
      before the date the amount of tax to be withheld is determined.  Once
      made, the election shall be irrevocable.  The fair market value of the
      shares to be withheld or delivered will be the Fair Market Value as of the
      date the amount of tax to be withheld is determined.  In the event a
      Participant elects to deliver or have the Company withhold shares of the
      relevant class of Common Stock pursuant to this Section 5.5(a), such
      delivery or withholding must be made subject to the conditions and
      pursuant to the procedures set forth in Section 5.3 with respect to the
      delivery or withholding of the relevant class of Common Stock in payment
      of the exercise price of Options.

                                      -5-<PAGE>
                                                                 EXHIBIT 10.5(i)

                  SIXTH AMENDMENT TO CREDIT AGREEMENT BY AND
                          BETWEEN INDIAN OIL COMPANY
                         AND BANK ONE, OKLAHOMA, N.A.

     THIS SIXTH AMENDMENT TO CREDIT AGREEMENT (the "Amendment") is made
effective as of the ___ day of July, 2000 by and between INDIAN OIL COMPANY, an
Oklahoma corporation (the "Borrower") and BANK ONE, OKLAHOMA, N.A. (the
"Lender").

                             W I T N E S S E T H:

     WHEREAS, on December 22, 1997, Borrower and Lender entered into that
certain Credit Agreement (the "Original Agreement") whereby Lender provided
Borrower with a reducing,  revolving line of credit in an amount, subject to a
Borrowing Base, which shall not exceed $50,000,000.00 as evidenced by the Note.

     WHEREAS, on August 10, 1998 Borrower and Lender amended the Original
Agreement for the first time (the "First Amendment") in order to: (i) change the
Debt Service Coverage ratio calculation; (ii) waive the occurrence of certain
events of default; and (iii) certain other changes more particularly set forth
therein;

     WHEREAS, on February 26, 1999, Borrower and Lender amended the Original
Agreement for the second time (the "Second Amendment") in order to (i) reduce
the Borrower's Borrowing Base availability from $24,000,000.00 to
$20,000,000.00; (ii) extend the deadline for Borrower to have completed a
$12,000,000.00 equity offering until March 1, 1999; (iii) extend the deadline
for Borrower to provide an audited financial statement for the fiscal year
ending December 31, 1997 until April 10, 1999; and  (iv) waive the occurrence of
certain events of default;

     WHEREAS, on March 31, 1999, Borrower and Lender amended the Agreement for
the third time (the "Third Amendment") in order to: (i) reset the Borrowing
Base, (ii) reset the Monthly Borrowing Base Reduction, (iii) restate the Debt
Service Coverage Ratio, and (iv) document such other amendments and waivers as
set forth in the Third Amendment;

     WHEREAS, on November 1st, 1999, Borrower and Lender amended the Agreement
for the fourth time (the "Fourth Amendment") in order to: (i) permit additional
subordinated debt, as described in the Fourth Amendment, (ii) to provide for
Unscheduled Redeterminations, (iii) to include commodity rate management
language and (iv) to document such other amendments, extensions and waivers as
set forth in the Fourth Amendment;

     WHEREAS, on January 1, 2000, Borrower and Lender amended the Agreement for
the fifth time (the "Fifth Amendment") in order to (i) renew and extend the
Note,  (ii) reset the
<PAGE>

Borrowing Base and the Monthly Borrowing Base Reduction, (iii) restate the Debt
Service Coverage Ratio and (iv) document such other amendments, extensions and
waivers as set forth in the Fifth Amendment (the Original Agreement as amended
by the First, Second, Third, and Fourth Amendments is referred to herein as the
"Agreement").

     WHEREAS, the obligations described in the Agreement are secured by, among
other things not specifically set forth herein, certain Oil and Gas Properties;
and

     WHEREAS, all capitalized terms not otherwise defined herein shall have
those meanings assigned to such terms in the Agreement;

     WHEREAS, Borrower and Lender now desire to amend the Agreement for the
sixth time in order to: (i) include a new $2,000,000 term loan facility,  (ii)
reset the Borrowing Base and the Monthly Borrowing Base Reduction, and (iii)
document such other amendments, extensions and waivers as set forth herein.

     NOW THEREFORE, in consideration of the mutual covenants and agreements
herein contained and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Borrower and the Lender hereby
agree to amend the agreement as follows:

     A.   CHANGES TO THE AGREEMENT.  The Agreement is hereby amended as follows:

          1.  The definition of "Note" set forth at Section 1.2 of the
                                 ----
Agreement, Additional Defined Terms, is hereby retitled as "Notes" and further
           ------------------------                         -----
amended and restated in its entirety in order to add the new term facility as
follows:

          "Notes" shall mean (i) the revolving promissory note made by the
           -----
     Borrower in the original face amount of $50,000,000.00 in the form attached
     hereto as Exhibit A with any blanks completed in conformity herewith (the
               ---------
     "Revolving Note")and (ii) that certain $2,000,000 term promissory note made
     by the Borrower in the form attached hereto as Exhibit A-1 (the "Term
                                                    -----------
     Note"), together with any and all renewals, extensions for any period,
     increases and rearrangements thereof.

          2.  Unless the context otherwise requires, all references in the
Agreement to the term "Note" including, without limitation, that reference at
Section 9.1(a), shall be deemed to hereinafter refer to the defined term
"Notes".  In those circumstances, if any, in which the context clearly refers to
a single "Note", such reference shall refer to the Revolving Note.

                                       2
<PAGE>

          3.  Article II of the Agreement, AMOUNT AND TERMS OF CREDIT FACILITY,
is hereby amended in order to add a new term loan facility by inserting an
additional Section numbered "Section 2.17" and entitled "Term Loan Facility"
which shall state as follows:

          2.17  Term Loan.  Subject to the terms and conditions herein
                ---------
     (including, without limitation, the right of Lender to decline to make an
     Advance so long as a Default or Event of Default exists) and relying on the
     representations and warranties contained in this Agreement, the Lender
     agrees, until the Maturity Date, to make an Advance, in immediately
     available funds, at the Principal Office to or for the benefit of Borrower
     from time to time in accordance with the terms and following receipt by
     Lender of a Request for Advance; provided, however, Lender shall not
     advance more than $2,000,000.00.  The Advance shall be made and the Term
     Note, as written evidence thereof, shall be maintained at the Principal
     Office.  This loan is expressly not revolving.  Once $2,000,000.00 has been
     advanced pursuant to this Term Loan Facility, no additional sums shall be
     advanced.

               2.17.1  Use of Proceeds.  Proceeds of the Advances pursuant to
                       ---------------
     this Term Loan Facility shall be used by the Borrower solely to support
     developmental drilling and/or leasing acquisitions (leasing investments
     will be limited to $350,000).

               2.17.2  Note.  The Advances under this Term Loan Facility shall
                       ----
     be evidenced by the Term Note, which Note shall (i) be payable to the order
     of Lender, and (ii) bear interest in accordance with Section 2.17.3 hereof.
                                                          --------------
     Notwithstanding the principal amount of the Note as stated on the face
     thereof, the amount of principal actually owing on the Note at any given
     time shall be the aggregate of all Advances theretofore made to Borrower
     hereunder, less all payments of principal theretofore actually received
     hereunder by Lender. Lender is authorized, but is not required, to endorse
     on a schedule attached to the Term Note appropriate notations evidencing
     the date and amount of each Advance as well as the amount of each payment
     made by Borrower thereunder.  This Term Note is expressly NOT a revolving
     line of credit.  Once sums are borrowed and repaid they cannot be
     reborrowed.

               2.17.3  Interest.  The unpaid principal balance of the Term
                       --------
     Note shall bear interest from the date of initial Advance to maturity at a
     rate per annum which shall from day to day be equal to (i) the Base Rate in
     effect from day to day, or (ii) the Highest Lawful Rate. The Base Rate
     shall be computed on the basis of a year of 360 days, but counting the
     actual days elapsed (including the first day but excluding the last day)
     during the period for which payable. Past due principal on the Term Note
     shall bear interest, and to the extent permitted by applicable law, past
     due interest shall bear interest at a rate per annum equal to the Default
     Rate.

                                       3
<PAGE>

               2.17.4  Repayment.  Beginning August 31, 2000 and continuing on
                       ---------
     the last day of each month thereafter through and including the Maturity
     Date, Borrower shall, at a minimum, pay accrued interest on any Advances
     subject to the Base Rate.  All principal plus all accrued but unpaid
     interest shall be due and payable in full on the Maturity Date, if there
     has not been an Event of Default which has resulted in all Obligations
     becoming immediately due and payable in accordance with Section 9.2 of this
                                                             -----------
     Agreement or before the Maturity Date if there has been an Event of Default
     which has resulted in all Obligations becoming immediately due and payable
     in accordance with Section 9.2 of this Agreement.
                        -----------

               2.17.5  Advances and Payments on Term Note.  The Lender is
                       ----------------------------------
     irrevocably authorized by the Borrower to account for Advances, payments,
     prepayments, etc. by any appropriate method with its customary
     documentation or other evidence thereof delivered to the Borrower within a
     reasonable time after each such Advances, payments, prepayments, etc.  The
     outstanding principal balance reflected by the accounting method utilized
     by Lender shall be deemed rebuttably presumptive evidence of the principal
     amount owing on the Term Note.  Interest provided for herein shall be
     calculated on unpaid sums actually advanced and outstanding pursuant to the
     terms of this Agreement and only for the period from the date or dates of
     such Advance pursuant to the Term Note until repayment.  The liability for
     payment of principal and interest evidenced by the Term Note shall be
     limited to principal amounts actually advanced and outstanding pursuant to
     this Agreement and interest on such amounts calculated in accordance with
     this Agreement.

               2.17.6  Voluntary Prepayments.  The Borrower shall have the right
                       ---------------------
     at any time or from time to time to prepay without premium or penalty, all
     or any part of the outstanding principal balance of the Term Note;
     provided, however, that no such prepayment shall, until all Obligations are
     -----------------
     fully paid and satisfied, excuse the payment as it becomes due of any
     payment provided for herein.

               2.17.7  Miscellaneous Provisions Concerning the Term Note.  The
                       -------------------------------------------------
     provisions concerning the Bank's right of offset and the maximum rate of
     interest set forth as Sections 2.13 and 2.14 shall apply with equal force
     and effect to the Term Loan Facility.

          4.  Except as set forth in Section 2.17.7, Sections 2.1 through 2.16
of the Agreement shall apply solely to the Revolving Note.  All references to
the term "Note" in such sections shall refer to the Revolving Note.

          5.  Article IV of the Agreement, CONDITIONS, is hereby amended in
order to add a conditions precedent to Advances under the term loan facility by
inserting an additional

                                       4
<PAGE>

Section numbered "Section 4.3" and entitled "Each Advance Under the Term Note"
                  -----------                --------------------------------
which shall state as follows:

          4.3  Each Advance Under the Note.  In addition to the conditions
               ---------------------------
     precedent stated in Section 4.1 having been fulfilled as of the Closing
                         -----------
     Date, the Lender shall not be obligated to make any Advance under the Term
     Note unless:

          (a) the Borrower shall have satisfied all conditions required for an
     Advance under the revolving promissory note as set forth in Section 4.2
     above;

          (b) Borrower shall have provided Lender with "AFE's" or other
     documentation or evidence substantiating the use of the proceeds to
     Lender's satisfaction.

          (c) all material matters incident to the consummation of the
     transactions hereby contemplated shall be satisfactory in the good faith
     judgment of the Lender.

          5.  The document attached hereto as Annex No. 1 shall be permanently
attached to the Agreement as Exhibit A-1.

     B.  NOTICES.  Pursuant to Section 2.9 and Section 7.2 of the Agreement, the
Borrower is hereby notified that effective as of  July 1, 2000, the Borrowing
Base has been redetermined at $16,270,000.00, which such amount shall be further
subject to a Monthly Borrowing Base Reduction of $220,000.00 beginning August 1,
2000.  The Borrowing Base, Monthly Borrowing Base Reduction and Half Life of the
Borrower's Oil and Gas Properties referenced herein shall remain in effect until
the earlier of the next scheduled Determination Date or (ii) an Unscheduled
Redetermination.

     C.  REPRESENTATIONS AND WARRANTIES

     Borrower hereby represents and warrants to Lender that:

          1.  Borrower is a corporation, duly organized, legally existing, and
in good standing under the laws of the State of Oklahoma, and is duly qualified
as a foreign corporation and in good standing in all other states wherein the
nature of its business or its assets make such qualification necessary.

          2.  Borrower's execution and delivery of this Amendment and
performance of its obligations hereunder: (a) are and will be within its
corporate powers; (b) are duly authorized by its board of directors; (c) are not
and will not be in contravention of any law, statute, rule or regulation, the
terms of its articles or certificates of incorporation and bylaws, nor of any
preferred stock provision, indenture, agreement or undertaking to which
Corporation or any of its properties are bound; (d) do not require any consent
or approval (including governmental)

                                       5
<PAGE>

which has not been given; and (e) will not result in the imposition of Liens,
charges or encumbrances on any of its properties or assets, except those in
favor of Lender hereunder.

          3.  This Amendment, when duly executed and delivered, will constitute
the legal, valid and binding obligations of each Borrower, enforceable in
accordance with its terms.

          4.  All financial statements, balance sheets, income statements and
other financial data which have been or are hereafter furnished to Lender by
each Borrower to induce Lender to make the loans hereunder due, and as to
subsequent financial statements will, fairly represent each Borrower's financial
condition as of the dates for which the same are furnished.  All such financial
statements, reports, papers and other data furnished to Lender are and will be,
when furnished: prepared in accordance with generally accepted accounting
principles consistently applied; accurate and correct in all material respects;
and complete insofar as completeness may be necessary to give Lender a true and
accurate knowledge of the subject matter.  Since the date of the last such
financial statements, no material adverse change has occurred in the operations
or condition, financial or otherwise and other financial data provided to
Lender; of either Borrower, nor, to the best of their knowledge, has either
Borrower incurred, any material liabilities or made any material investment or
guarantees, direct or contingent, in any single case or in the aggregate, which
has not been disclosed to Lender.

          5.  The Borrower is the sole and lawful owner of the Collateral,
pledged, mortgaged or assigned by it, and Borrower has, and as to after acquired
property or New Properties will have, good right to cause the Collateral to be
hypothecated to Lender as security for the Obligations.

          6.  All of Borrower's other representations and warranties set forth
in Sections 5.1 through 5.22 of the Agreement are true and correct on and as of
the date hereof with the same effect as though made and repeated by Borrower as
of the date hereof.

     D.  CONDITIONS

     Lender's obligations under the Agreement, as hereby amended, is subject to
the following conditions:

          1.  Lender and Borrower shall have executed and delivered this
Amendment.

          2.  Borrower shall have executed and delivered to Lender the Term
Note.

          3.  Lender shall have received an estoppel certificate from Coral or
other evidence acceptable to Lender that the Agreement and Plan of Merger is
still in effect and that there are currently no defaults or events of default
pertaining thereto.

                                       6
<PAGE>

          4.  Lender shall have received evidence acceptable to Lender that both
MidFirst and Coral consent and/or approve of the renewals, modifications,
amendments set forth herein.

          5   Borrower's representations and warranties set forth in Section C
hereof shall be true and correct on and as of the date hereof, and the date of
any subsequent advance with the same effect as though such representation and
warranty had been on and as of such date.

          6.  Borrower shall have satisfied all conditions set forth in Section
4.1 of the Agreement.

          7.  No Event of Default nor any event which, with the giving of notice
or lapse of time, would constitute an Event of Default shall have occurred and
be continuing which has not been waived by Lender.

     E.  OTHER COVENANTS AND MISCELLANEOUS TERMS

          1.  Except as expressly amended and supplemented hereby, the Agreement
shall remain unchanged and in full force and effect, and the same is hereby
ratified and extended.

          2.  Obligations, including but not limited to the indebtedness
evidenced by the Note executed in conjunction with the Fifth Amendment to the
Agreement, shall continue to be secured by the Collateral, without interruption
or impairment of any kind.

          3.  Borrower shall make, execute or endorse, and acknowledge and
deliver or file or cause the same to be done, all such vouchers, invoices,
notices, certifications and additional agreements, undertakings, conveyances,
deeds of trusts, mortgages, transfers, assignments, financing statements or
other assurances, and take any and all such other action, as Lender may, from
time to time, deem reasonably necessary or proper in connection with any of the
Loan Documents and the obligations of Borrower assuring and confirming unto
Lender all or any part of the security for any such obligation.  In connection
herewith, Lender may require Borrower to execute additional mortgages or deeds
of trust in order to provide mortgage coverage of at least eighty-five percent
of the Borrower's Oil and Gas Properties and provide evidence of title to, at
least, eighty-five percent of the total properties mortgaged to Lender.  The
additional mortgages shall be provided to Lender within 30 days of the date
hereof and the additional evidence of title shall be provided to Lender within
60 days of the date hereof.

          4.  The Borrower hereby agrees to pay all reasonable attorney fees and
legal expenses incurred by Lender in preparation, execution and implementation
of this Amendment and any mortgages, deeds of trust, security agreements, pledge
agreements or any amendments thereto.

                                       7
<PAGE>

          5.  This Amendment shall be construed in accordance with and governed
by the laws of the State of Oklahoma, and shall be binding on and inure to the
benefit of the Borrower and Lender, and their respective successors and assigns.
All obligations of the Borrower under the Agreement and all rights of Lender and
any other holder of the Notes, whether expressed herein or in any Note, shall be
in addition to and not in limitation of those provided by applicable law.
Borrower irrevocably agrees that, subject to Lender's sole election, all suits
or proceedings arising from or related to the Agreement, as amended, or the
Notes may be litigated in courts (whether State or Federal) sitting in
Oklahoma City, Oklahoma, and the Borrower hereby irrevocably waives any
objection to such jurisdiction and venue.

          6.  This Amendment may be executed in as many counterparts as are
deemed necessary or convenient, and it shall not be necessary for the signature
of more than any one party to appear on any single counterpart.  Each
counterpart shall be deemed an original, but all shall be construed together as
one and the same instrument.  The failure of any party to sign shall not affect
or limit the liability of any party executing any such counterpart.

     BORROWER:      INDIAN OIL COMPANY,
                              an Oklahoma corporation

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

                              By: John K. Penton
                              Title: Executive Vice President

     LENDER:        BANK ONE, OKLAHOMA, N.A.

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

                              By: Coy Gallatin
                              Title: Vice President

                                       8

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