Document:

ANSCHUTZ
                          INVESTMENT COMPANY

555 SEVENTEENTH STREET O SUITE 2400 O DENVER, COLORADO 80202 O 303-298-1000
O FAX 303-299-1333

                             EXHIBIT 10.4

                            March 21, 2000

Rentech, Inc.
1331 17th Street, Suite 720
Denver, Colorado  80202
Attention:  Mr. Ronald C. Butz, Vice President & COO

         Re:      Transactions among Rentech, Inc., Anschutz Investment Company
                  and Forest Oil Company

Dear Mr. Butz:

         Reference is made to the Purchase Agreement (the "Purchase Agreement"),
dated as of March 18, 2000, between Anschutz Investment Company ("Anschutz") and
Rentech, Inc. (the "Company"); the Option to Purchase Shares of Common Stock of
the Company, dated as of March 18, 2000, by and between Anschutz and the
Company, which option expires on December 31, 2001 (the "2001 Option"); the
Option to Purchase Shares of Common Stock of the Company, dated as of March 18,
2000, by and between Anschutz and the Company, which option expires on December
31, 2004 (the "2004 Option" and together with the 2001 Option, the "Options"));
and the Registration Rights Agreement (the "Registration Rights Agreement"),
dated as of March 18, 2000, by and among the Company, Forest Oil Company and
Anschutz. The Purchase Agreement, the Options and the Registrations Rights
Agreement are referred to herein as the "Agreements."

         We hereby notify you that we have assigned to A.C.E. Investment
Partnership, a Colorado general partnership ("A.C.E."), certain rights, and
A.C.E. has assumed certain obligations, under the Agreements. We have assigned
and A.C.E. has assumed all obligations with respect to, (a) the right to
purchase 61,250 shares of the Company's common stock pursuant to the terms of
the Purchase Agreement, (b) the right to purchase 122,500 shares of the
Company's common stock pursuant to the terms of the 2001 Option, (c) the right
to purchase 61,250 shares of the Company's common stock pursuant to the terms of
the 2004 Option and (d) the registration rights described in the Registration
Rights Agreement with respect to the shares of common stock described in clauses
(a) through (c).

         In light of the foregoing, we have enclosed the Options and ask that
you deliver to us (i) two new 2001 Options reflecting our right to purchase
1,877,500 shares of the Company's common stock and the right of A.C.E. to
purchase 122,500 shares of the Company's common stock and (ii) two new 2004
Options reflecting our right to purchase 938,750 shares of the Company's common
stock and the right of A.C.E. to purchase 61,250 shares of the Company's common
stock. We will deliver the appropriate options to A.C.E. upon receipt thereof.

<PAGE>

         Rentech, Inc.
         March 21, 2000
         Page 2

         In the event that you are required under any of the Agreements to
provide notice to A.C.E., you may deliver such notice care of Anschutz
Investment Company.

                                                  Very truly yours,

                                                  ANSCHUTZ INVESTMENT COMPANY

                                                  By:  /s/ CLIFFORD HICKEY
                                                       -------------------------
                                                           Clifford Hickey
                                                           Vice President

cc:  A.C.E. Investment Partnership
       Forest Oil CompanyACQUISITION OF THE 49% RIGHTS TO NET PROFITS AGREEMENT

                 This Acquisition of the 49% rights to net profits Agreement
        (the Agreement) is made and entered into this 27th day of February, 2000
        by and between Prof. Oleg Figovsky with offices located 3A Shimkin
        Street #l Haifa Israel 34750 (referred to herein as the ("Inventor") and
        EUROTECH Ltd., a District of Columbia corporation with offices at 1216
        16th Street, NW Washington DC 20036 USA (`Company").

                 A. Inventor is the developer of certain technologies known as
        LEM, RubCon, HNIPU, Electronic Glues and anticorrosive additives (the
        `Technology"), rights to which were sold in their entirety by the
        Inventor to the Company in accordance to the agreements previously
        signed and executed in exchange to the royalty equal to 49% of the net
        revenues generated from sales of the said technologies as provided in
        the agreements attached hereto in Exhibit A.

                 B. The Inventor and the Company believe that an amendment to
        these agreements would better reflect the nature of the ongoing and the
        future relations between the Company and the Inventor and have agreed to
        amend the original agreements as provided in paragraph (C)of this
        Agreement.

                 C. The Inventor is willing to fully waive his rights to the 49%
        net profits as stipulated in the paragraph (2) "Consideration" and all
        relevant paragraphs of the original agreements attached hereto in
        exchange to a one time sum of $235,000 (two hundred and thirty five
        thousand) paid by the Company to the Inventor within 30 days of signing
        this contract and one percent (1%) royalty from the gross revenues
        generated by the sales of the Technology for the period of the 15 years.

                  D. All other provisions of the original contracts shall stay
         the same.

                                           Company    /s/ Don V. Hahnfeldt
                                                      --------------------------
                                                      Don V. Hahnfeldt
                                                      Chief Executive Officer

                                                                     SEAL

                                           Inventor   /S/ Oleg Figovsky
                                                      --------------------------
                                                      Oleg Figovsky

        EXHIBIT A

         THE ORIGINAL AGREEMENTS ON PURCHASE OF THE TECHNOLOGY.

                 The Terms and Conditions are described in the attached
Agreements.[EUROTECH LTD. LOGO HERE]

                                                         February 25, 2000

        Mr. Neil T. Chau, Managing Member
        Encore Capital Management L.L.C.
        12007 Sunrise Valley Drive, Suite 460
        Reston, Virginia 20191

        Dear Mr. Chau:

        Thank you for your willingness to reconsider new terms for surviving
        agreements between Encore and Eurotech. Following are terms agreeable to
        EUROTECH, Ltd. that have been verbally concurred with by Encore, and
        formally proposed as amendments to existing Agreements:

                     That Encore may convert the Convertible Debentures of
                          Agreement of July 1998 with an existing ceiling of
                          $1,06. As of March 1, 2000 /S/

                     That Encore will institute a floor price of $2.00 on all
                          other remaining Convertible Debentures.

                     That other terms and conditions of convertible debentures
                          and warrants remain as agreed in previous
                          agreements.

                     That Encore accept from Eurotech 300,000 shares of common
                          stock as payment for all outstanding penalties with
                          interest. To be issued as of March 1, 2000 /S/

                     That Eurotech has paid the $400,000 loan and interest.

                     That Eurotech brought interest payments on remaining
                          agreements current as of December 31, 1999.

                     That Eurotech will issue 250,000 three-year warrants to
                          Encore with strike price of $3.00. To be issued as
                          of March 1, 2000 /S/

        Your cooperation through this period of financial restructuring is
        greatly appreciated as it continues to be vital to EUROTECH, Ltd.
        success in delivering EKOR and other very promising technologies.

        Sincerely,

        /s/ Don V. Hahnfeldt
        --------------------
        Don V. Hahnfeldt
        President, EUROTECH, Ltd.

        Agreed and accepted by:

        /S/ Neil T. Chau
        Neil T. Chau, Encore Capital Management, L.L.C./ date

                                        1216 16th St. N.W., Washington, DC 20036
                                        Phone (202) 466-5448 Fax: (202) 466-5591SECOND AMENDED AND RESTATED
                    CERTIFICATE OF DESIGNATIONS, PREFERENCES
                          AND RIGHTS OF PREFERRED STOCK
                         OF MICROTEL INTERNATIONAL INC.,
                             A DELAWARE CORPORATION

          The undersigned, Carmine T. Oliva, hereby certifies that:

          A. He is the duly elected and acting President of MicroTel
International Inc., a Delaware corporation (the "Corporation").

          B. Pursuant to authority given by the corporation's Certificate of
Incorporation, and in accordance with the provisions of Section 151 of the
General Corporation Law of the State of Delaware, the Board of Directors of the
Corporation has duly adopted the following recitals and resolutions:

          WHEREAS, the Certificate of Incorporation of the Corporation provides
for two classes of shares known as Common Stock and Preferred Stock;

          WHEREAS, the Board of Directors of the Corporation is authorized by
the Certificate of Incorporation to provide for the issuance of the shares of
Preferred Stock in series, and by filing a certificate pursuant to the
applicable law of the State of Delaware, to establish from time to time the
number of shares to be included in each such series, and to fix the designation,
powers, preferences and rights of the shares of each such series and the
qualifications, limitations or restrictions thereof; and

          NOW, THEREFORE, BE IT RESOLVED, that the Board of Directors deems it
advisable to adopt, and hereby does adopt, the Corporation's Second Amended and
Restated Certificate of Designations, Preferences and Rights of Series A
Preferred Stock of MicroTel International, Inc., a Delaware corporation:

          A. DESIGNATION. One series of Preferred Stock, designated Series A
Preferred Stock, is hereby provided for, which shares shall have the rights,
privileges and preferences set forth below.

          B. AUTHORIZED NUMBER. The number of shares constituting the Series A
Preferred Stock shall be 200, par value .01 per share.

          C. DIVIDEND PROVISIONS. The holders of shares of Series A Preferred
Stock shall not be entitled to receive dividends.

          D. LIQUIDATION PREFERENCE.

                  (a) In the event of any liquidation, dissolution or winding up
of the Corporation, either voluntary or involuntary, the holders of shares of
Series A Preferred Stock shall be entitled to receive, prior and in preference
to any distribution of any of the assets of this corporation to the holders of
the Common Stock by reason of their ownership, an amount per share equal to
$10,000 (the "Stated Value") for each outstanding share of Series A Preferred
Stock. If upon the occurrence of such event, the assets and funds thus
distributed among the holders of the Series A Preferred Stock shall be

<PAGE>

insufficient to permit the payment to such holders of the full aforesaid
preferential amounts, then the entire assets and funds of the corporation
legally available for distribution shall be distributed ratably among the
holders of the Series A Preferred Stock on a share-by-share basis in proportion
to the aggregate preferential amounts of each such series of Preferred Stock.

                  (b) A consolidation or merger of the Corporation with or into
any other corporation or corporations, or a sale, conveyance or disposition of
all or substantially all of the assets of this corporation or the effectuation
by the Corporation of a transaction or series of related transactions in which
more than 50% of the voting power of the Corporation is disposed of, shall not
be deemed to be a liquidation, dissolution or winding up within the meaning of
this Section D but shall instead be treated pursuant to Section B hereto.

         E. CONVERSION. The holders of the Series A Preferred Shares shall have
conversion rights as follows (the "Conversion Rights"):

                  (1) CONVERSION RIGHTS.

                           (i) Each Series A Preferred Share shall be
convertible, at the option of the holders of such shares, at any time, at the
office of the Corporation or any transfer agent for the Series A Preferred
Shares, into 50,530 fully paid and non-assessable Common Shares of the
Corporation.

                           (ii) In the event of a call for redemption of any
Series A Preferred Shares pursuant to Section F hereof, each holder of any
Series A Preferred Shares shall have the right to exercise the conversion rights
set forth in this Section E and the right to convert each share shall cease as
to the shares designated for redemption as of the close of business on the
business day immediately prior to the redemption date, unless default is made in
payment of the redemption price. If the Corporation has received a notice of
conversion with respect to any Series A Preferred Shares the Corporation may not
redeem such Series A Preferred Shares provided the Series A Preferred Shares are
delivered for conversion as set forth in Section E(2).

                  (2) MECHANICS OF CONVERSION.

                           (i) No fractional shares of Common Stock shall be
issued upon conversion of the Series A Preferred Shares. In lieu of any
fractional share to which the holder would otherwise be entitled, the
Corporation shall round up to the nearest whole share. In the case of a dispute
as to the calculation of the Conversion Rate, the Corporations calculation shall
be deemed conclusive absent manifest error. In order to convert Series A
Preferred Shares into full shares of Common Stock, the holder shall surrender
the certificate or certificates therefor, duly endorsed, by either overnight
courier or 2-day courier, to the office of the Corporation for the Series A
Preferred Shares, and shall give written notice to the Corporation at such
office that the holder elects to convert the same, the number of shares of
Series A Preferred Shares so converted and a calculation of the Conversion Rate
(with an advance copy of the certificate(s) and the notice by facsimile);
provided, however, that the Corporation shall not be obligated to deliver
certificates evidencing the shares of Common Stock issuable upon such conversion
unless certificates evidencing such Series A Preferred Shares are delivered to

                                        2
<PAGE>

the Corporation as provided above, or the holder notifies the Corporation that
such certificates have been lost, stolen or destroyed and executes an agreement
satisfactory to the Corporation to indemnify the Corporation from any loss
incurred by it in connection with such certificates.

                           (ii) The Corporation shall use reasonable efforts to
cause to be issued and delivered within two (2) business days after delivery to
the Corporation of such Series A Preferred Shares, or after such agreement and
indemnification, to such holder of Series A Preferred Shares at the address of
the holder on the stock books of the Corporation, a certificate or certificates
for the number of shares of Common Stock to which he shall be entitled as
aforesaid. The date on which notice of conversion is given (the "Date of
Conversion") shall be deemed to be the date set forth in such notice of
conversion provided the original Series A Preferred Shares to be converted are
received by the Corporation within five (5) business days thereafter and the
person or persons entitled to receive the shares of Common Stock issuable upon
such conversion shall be treated for all purposes as the record holder or
holders of such shares of Common Stock on such date. If the original Series A
Preferred Shares to be converted are not received by the Corporation within five
(5) business days after the Conversion, the notice of conversion shall become
null and void.

                  (3) CONVERSION PRICE ADJUSTMENTS. The number of Common Shares
issuable upon conversion as set forth in Section E(l)(i) shall be appropriately
adjusted to reflect, as deemed equitable and appropriate by the Corporation, any
stock dividend, stock split or share combination of the Common Stock. In the
event of a merger, reorganization, recapitalization or similar event of or with
respect to the Corporation (a "Corporate Change") (other than a Corporate Change
in which all or substantially all of the consideration received by the holders
of the Company's equity securities upon such Corporate Change consists of cash
or assets other than securities issued by the acquiring entity or any affiliate
thereof), the Series A Preferred Shares shall be convertible into such class and
type of securities as the Holder would have received had the Holder converted
the Series A Preferred Shares immediately prior to such Corporate Change, as
appropriately adjusted to equitably reflect the conversion price and any stock
dividend, stock split or share combination of the common stock after such
corporate event.

                  (4) RESERVATION OF STOCK ISSUABLE UPON CONVERSION. The
Corporation shall at all times reserve and keep available out of its authorized
but unissued Common Shares solely for the purpose of effecting the conversion of
the Series A Preferred Shares such number of its Common Shares as shall from
time to time be sufficient to effect the conversion of all outstanding Series A
Preferred Shares; and if at any time the number of authorized but unissued
Common Shares shall not be sufficient to effect the conversion of all then
outstanding Series A Preferred Shares, in addition to such other remedies as
shall be available to the holder of such Series A Preferred Shares, the
Corporation will take such corporate action as may, in the opinion of its
counsel, be necessary to increase its authorized but unissued Common Shares to
such number of shares as shall be sufficient for such purposes.

         F. REDEMPTION OF SERIES A PREFERRED SHARES.

                  (1) OPTIONAL REDEMPTION. The Corporation may redeem all
outstanding and unconverted Series A Preferred Shares for cash at a per share
price equal to $11,500 (115% of the Stated Value) for each Series A Preferred
Share by giving written notice to Buyer at least twenty (20) days in advance of

                                       3
<PAGE>

such redemption. Notwithstanding the above, the Corporation may not redeem the
Preferred Shares unless there are sufficient authorized and reserved Common
Shares to permit conversion by the holders thereof within such twenty (20) day
period. If the Corporation has received a notice of conversion with respect to
any Series A Preferred Shares, the Corporation may not redeem such Series A
Preferred Shares provided the Series A Preferred Shares are delivered for
conversion as set forth in Section E(2) during the notice period prior to the
redemption date as set forth in F(3)(ii) below.

                  (2) MANDATORY REDEMPTION. On May 22, 2003, the Corporation
shall redeem all Series A Preferred Shares then outstanding, by the payment
therefor of the redemption price of $11,500 per share.

                  (3) MANNER OF REDEMPTION OF SERIES A PREFERRED SHARES.

                           (i) If less than all of the outstanding Series A
Preferred Shares shall be called for redemption, the particular shares of such
series to be redeemed shall be selected by lot or by such other equitable manner
as may be prescribed by resolution of the Board of Directors.

                           (ii) Notice of redemption of any Series A Preferred
Shares shall be given by the Corporation by fax or other written communication,
at least twenty (20) days prior to the date fixed by the Board of Directors of
the Corporation for redemption (herein called the "redemption date"), to the
holders of record of the shares to be redeemed at their respective addresses
then appearing on the records of the Corporation. The notice of the redemption
shall state:

                                (A) the redemption date,

                                (B) the redemption price (which must be paid
within five (5) business days after the date of redemption),

                                (C) whether the redemption is an optional
redemption or a mandatory redemption,

                                (D) if less than all outstanding Series A
Preferred Shares are to be redeemed, the identification of the Series A
Preferred Shares to be redeemed,

                                (E) the conversion rate on the date of the
notice,

                                (F) that on the redemption date the redemption
price will become due and payable upon each Series A Preferred Shares to be
redeemed and the right to convert each share of Series A Preferred Share shall
cease as of the close of business on the business day prior to the redemption
date, unless default shall be made in the payment of the redemption price, and

                                (G) the place or places where such Series A
Preferred Shares to be redeemed are to be surrendered for payment of the
redemption price.

                  (4) FAILURE TO REDEEM. If the Corporation fails to pay the
redemption price after calling any Series A Preferred Shares for optional
redemption under Section F(l), the Corporation shall have no further right to
redeem Series A Preferred Shares under Section F(l).

                                       4
<PAGE>

                  (5) REACQUIRED SHARES. Any shares of the Series A Preferred
Stock converted, redeemed or purchased or otherwise acquired by the Corporation
in any manner whatsoever shall be retired and cancelled promptly after the
acquisition thereof. All such shares shall upon their cancellation become
authorized but unissued shares of Series A Preferred Stock and may be reissued
at the direction of the Corporation subject to the conditions or restrictions on
issuance set forth herein.

         G. CORPORATE EVENTS. In the event of (i) any declaration by the
Corporation of a record date of the holders of any class of securities for the
purpose of determining the holders thereof who are entitled to receive any
dividend (other than cash dividend) or other distribution or (ii) any capital
reorganization of the Corporation, any reclassification or recapitalization of
the capital stock of the Corporation, any merger or consolidation of the
Corporation, and any transfer of all or substantially all of the assets of the
Corporation to any other Corporation, or any other entity or person, or any
voluntary or involuntary dissolution, liquidation or winding up of the
Corporation, the Corporation shall mail to each holder of Series A Preferred
Shares at least twenty (20) days prior to the record date specified therein, a
notice specifying (A) the date on which any such record is to be declared for
the purpose of such dividend or distribution and a description of such dividend
or distribution, (B) the date on which any such reorganization,
reclassification, transfer, consolidation, merger, dissolution, liquidation or
winding up is expected to become effective and (C) the time, if any, that is to
be fixed, as to when the holders of record of Common Stock (or other securities)
will receive for securities or other property deliverable upon such
reorganization, reclassification, transfer, consolidation, merger, dissolution
or winding up.

         H. VOTING RIGHTS.

                  (1) The Holders of the Series A Preferred Shares shall not
have any voting rights except as set forth below or as otherwise from time to
time required by law.
                  (2) To the extent that under Delaware law the vote of the
holders of the Series A Preferred Shares, voting separately as a class, is
required to authorize a given action of the Corporation, the affirmative vote or
consent of the holders of at least a majority of the outstanding Series A
Preferred Shares shall constitute the approval of such action by the class. To
the extent that under Delaware law the holders of the Series A Preferred Shares
are entitled to vote on a matter with holders of Common Stock voting together as
one class, each Series A Preferred Shares shall be entitled to a number of votes
equal to the number of shares of Common Stock into which it is then convertible
using the record date for the taking of such vote of stockholders as of the date
of determination. Holders of the Series A Preferred Shares shall be entitled to
notice of all shareholder meetings or written consents with respect to which
they would be entitled to vote, which notice would be provided pursuant to the
Corporation's bylaws and applicable statutes.

         I. PROTECTIVE PROVISIONS. So long as the Series A Preferred Shares are
outstanding, the Corporation shall not take any action that would impair the
rights of the holders of the Series A Preferred Shares set forth herein and
shall not without first obtaining the approval (by vote or written consent, as
provided by law) of the holders of at least a majority in aggregate principal
amount of the Series A Preferred Shares then outstanding:

                                        5
<PAGE>

                  (1) Alter or change the rights, preferences or privileges of
the Series A Preferred Shares so as to affect adversely the Series A Preferred
Shares.

                  (2) For a period of eight (8) months from the issuance of the
Series A Preferred Shares, create any new class or series of stock which ranks
prior to or PARI PASSU to the Series A Preferred Shares with respect to
liquidation preference, other than any additional series of Preferred Shares
issued for a purchase price not to exceed $2 million, which may rank PARI PASSU.

                  (3) Do any act or thing which would result in taxation of the
holders of Series A Preferred Shares under Section 305 of the Internal Revenue
Code of 1985, as amended (or any comparable provision of the Internal Revenue
Code as hereafter from time to time amended).

                                       6

<PAGE>

          IN WITNESS WHEREOF, the Corporation has caused this Certificate to be
signed by its authorized officer as of December 23, 1999.

                                       MICROTEL INTERNATIONAL INC.
                                       By: /S/ Carmine T. Oliva
                                           -------------------------------------
                                           Carmine T. Oliva
                                           President and Chief Executive Officer

                                       7

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