Document:

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                       MORGAN STANLEY SELECT EQUITY TRUST
                          REIT PORTFOLIO SERIES 2001-3
                            REFERENCE TRUST AGREEMENT

          This Reference Trust Agreement dated July 11, 2001 between MORGAN
STANLEY DW INC., as Depositor, and The Chase Manhattan Bank, as Trustee, sets
forth certain provisions in full and incorporates other provisions by reference
to the document entitled "Sears Equity Investment Trust, Trust Indenture and
Agreement" dated January 22, 1991, as amended on March 16, 1993, July 18, 1995
and December 30, 1997 (the "Basic Agreement"). Such provisions as are
incorporated by reference constitute a single instrument (the "Indenture").

                                WITNESSETH THAT:

          In consideration of the premises and of the mutual agreements herein
contained, the Depositor and the Trustee agree as follows:

                                       I.

                     STANDARD TERMS AND CONDITIONS OF TRUST

          Subject to the provisions of Part II hereof, all the provisions
contained in the Basic Agreement are herein incorporated by reference in their
entirety and shall be deemed to be a part of this instrument as fully and to the
same extent as though said provisions had been set forth in full in this
instrument except that the Basic Agreement is hereby amended in the following
manner:

          A.   Article I, Section 1.01, paragraph (29) defining "Trustee" shall
     be amended as follows:

          "'Trustee' shall mean The Chase Manhattan Bank, or any successor
          trustee appointed as hereinafter provided."

          B.   Reference to United States Trust Company of New York in its
     capacity as Trustee is replaced by The Chase Manhattan Bank throughout the
     Basic Agreement.

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          C.   Reference to "Morgan Stanley Dean Witter Select Equity Trust" is
     replaced by "Morgan Stanley Select Equity Trust".

          D.   Section 2.03 is amended to add the following to the end of the
     first paragraph thereof. The number of Units may be increased through a
     split of the Units or decreased through a reverse split thereof, as
     directed by the Depositor, which revised number of Units shall be recorded
     by Trustee on its books.

          E.   Section 3.01 is amended to substitute the following:

          SECTION 3.01. INITIAL COST The costs of organizing the Trust and sale
     of the Trust Units shall, to the extent of the expenses reimbursable to the
     Depositor provided below, be borne by the Unit Holders, PROVIDED, HOWEVER,
     that, to the extent all of such costs are not borne by Unit Holders, the
     amount of such costs not borne by Unit Holders shall be borne by the
     Depositor and, PROVIDED FURTHER, HOWEVER, that the liability on the part of
     the Depositor under this Section shall not include any fees or other
     expenses incurred in connection with the administration of the Trust
     subsequent to the deposit referred to in Section 2.01. Upon notification
     from the Depositor that the primary offering period is concluded, the
     Trustee shall withdraw from the Account or Accounts specified in the
     Prospectus or, if no Account is therein specified, from the Principal
     Account, and pay to the Depositor the Depositor's reimbursable expenses of
     organizing the Trust and sale of the Trust Units in an amount certified to
     the Trustee by the Depositor. If the balance of the Principal Account is
     insufficient to make such withdrawal, the Trustee shall, as directed by the
     Depositor, sell Securities identified by the Depositor, or distribute to
     the Depositor Securities having a value, as determined under Section 4.01
     as of the date of distribution, sufficient for such reimbursement. The
     reimbursement provided for in this Section shall be for the account of the
     Unitholders of record at the conclusion of the primary offering period and
     shall not be reflected in the computation of the Unit Value prior thereto.
     As used herein, the Depositor's reimbursable expenses of organizing the
     Trust and sale of the Trust Units shall include the cost of the initial
     preparation and typesetting of the registration statement, prospectuses
     (including preliminary prospectuses), the indenture, and other documents
     relating to the Trust, SEC

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     and state blue sky registration fees, the cost of the initial valuation of
     the portfolio and audit of the Trust, the initial fees and expenses of the
     Trustee, and legal and other out-of- pocket expenses related thereto, but
     not including the expenses incurred in the printing of preliminary
     prospectuses and prospectuses, expenses incurred in the preparation and
     printing of brochures and other advertising materials and any other selling
     expenses. Any cash which the Depositor has identified as to be used for
     reimbursement of expenses pursuant to this Section shall be reserved by the
     Trustee for such purpose and shall not be subject to distribution or,
     unless the Depositor otherwise directs, used for payment of redemptions in
     excess of the per-Unit amount allocable to Units tendered for redemption.

          F.   The third through fifth paragraphs of Section 3.05 shall be
     amended to provide as follows:

          On each Distribution Date or within a reasonable period of time
     thereafter, the Trustee shall distribute by mail to each Unit Holder of
     record at the close of business on the preceding Record Date at his address
     appearing on the registration books of the Trustee such Unit Holder's
     income distribution, computed as hereinafter provided, plus such holder's
     pro rata share of the cash balance of the Principal Account, each computed
     as of the preceding Record Date; provided, however, that funds credited to
     the Principal Account in the event of the failure of consummation of a
     contract to purchase Securities pursuant to Section 2.01 hereof, funds
     representing the proceeds of the sale of Securities pursuant to Section
     3.08 hereof, and funds representing the proceeds of the sale of Securities
     under Sections 5.02 or 6.04 in excess of the amounts needed for the
     purposes of said Sections shall not be distributed until the next
     Distribution Date or at such earlier date as shall be determined by the
     Trustee. The Trustee shall not be required to make a distribution from the
     Principal Amount unless the cash balance on deposit therein available for
     distribution shall be sufficient to distribute at least $1.00 per Unit in
     the case of Units initially offered at approximately $1,000 or a
     proportionately lower amount in the case of Units initially offered at less
     that $1,000 (E.G. $.001 per Unit in the case of Units initially offered at
     approximately $1.00).

          The Trustee shall, as of each Record Date, compute and report to the
     Depositor the per-Unit amount of the

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     monthly income distribution to be made on the next following Distribution
     Date (the "Monthly Income Distribution") by (i) estimating the annual
     income of the Trust for the ensuing twelve months (by reference to the most
     recent distributions made on Securities and any information received by the
     Trustee with respect to future dividends or other income), (ii) deducting
     therefrom the estimated costs and expenses to be incurred during the
     twelve-month period for which such income has been estimated and (iii)
     dividing the amount so obtained by the result of 12 multiplied by the
     number of Units outstanding on such Record Date. However, unless the
     Trustee or the Sponsor determines that the Monthly Income Distribution
     should be adjusted as provided hereafter, the amount of the Monthly Income
     Distribution shall be the amount computed by the Trustee on the most recent
     prior, or concurrently occurring, Quarterly Computation Date (such
     "Quarterly Computation Date" being the first Record Date and each Record
     Date occurring at three-month intervals thereafter). The Trustee will
     adjust the amount of the Monthly Income Distribution computed on each
     Quarterly Computation Date to reconcile, over the ensuing three Monthly
     Income Distributions, any variance between net income and distributions
     made during the preceding three months. Notwithstanding the preceding, the
     Trustee may reduce the amount of any Monthly Income Distribution in the
     event the Trustee or the Sponsor determines that such adjustment is
     necessary to avoid, or to respond to, a significant discrepancy between
     estimated and actual net income. Notwithstanding the foregoing, the Trustee
     may adjust the amount of the Monthly Income Distribution in order to
     maintain an average annual cash balance in the Income Account of $0.

          In the event the amount on deposit in the Income Account of the Trust
     on a Distribution Date is not sufficient for the payment of the amount of
     income to be distributed on the basis of the aforesaid computation, the
     Trustee shall advance out of its own funds and cause to be deposited in and
     credited to the Income Account such amount as may be required to permit
     payment of the income distribution to be made on such Distribution Date and
     shall be entitled to be reimbursed, without interest, out of the income
     subsequently received on the first Record Date following the date of such
     advance on which such reimbursement may be made without reducing the cash
     balance of the Income Account to an amount less than that required for the
     next ensuing distribution. The Trustee shall have a priority claim on
     any dividends or

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     other income received by the Trust to the extent of all amounts advanced by
     it pursuant to this paragraph, and such advances shall be considered a lien
     on the Trust prior to the interest of Unit Holders.

          The amounts to be distributed to each Unit Holder shall be that
     per-Unit income distribution and pro rata share of the cash balance of the
     Principal Account of the Trust, computed as hereinabove provided, as shall
     be represented by the Units owned by such Unit Holder as evidenced by the
     record books of the Trustee as of the applicable Record Date.

          In computing the distribution to be made to any Unit Holder, fractions
     of one cent shall be omitted. After any such distribution, any cash balance
     remaining in the Income Account or the Principal Account shall be held in
     the same manner as other amounts subsequently deposited in each of such
     Accounts, respectively.

          G.   Section 3.15 shall be amended by adding the following to the end
     thereof:

          The Depositor represents that the price paid by any Unit holder for
     Units acquired through reinvestment of Trust distributions will be reduced
     by the aggregate amount of unpaid deferred sales charge at the time of the
     purchase to offset any subsequent collection by the Depositor of deferred
     sales charge in respect of the Units so acquired.

          H.   Reference to "Dean Witter Reynolds Inc." is replaced by "Morgan
     Stanley DW Inc."

                                       II.

                      SPECIAL TERMS AND CONDITIONS OF TRUST

          The following special terms and conditions are hereby agreed to:

          A.   The Trust is denominated Morgan Stanley Select
     Equity Trust REIT Portfolio Series 2001-3 (the "REIT"
     Trust").

          B.   The publicly traded stocks listed in Schedule A hereto are those
     which, subject to the terms of this

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     Indenture, have been or are to be deposited in trust under this Indenture.

          C.   The term, "Depositor" shall mean Morgan Stanley DW Inc.

          D.   The aggregate number of Units referred to in Sections 2.03 and
     9.01 of the Basic Agreement is 24,899 for the REIT Trust.

          E.   A Unit is hereby declared initially equal to 1/24,899th for the
     REIT Trust.

          F.   The term "In-Kind Distribution Date" shall mean July 18, 2003.

          G.   The term "Record Date" shall mean monthly on the 1st day of each
     month beginning August 1, 2001.

          H.   The term "Distribution Dates" shall mean monthly on the 15th day
     of each month beginning August 15, 2001.

          I.   The term "Termination Date" shall mean August 29, 2003.

          J.   The Depositor's Annual Portfolio Supervision Fee shall be a
     maximum of $0.25 per 100 Units.

          K.   The Trustee's annual fee as defined in Section 6.04 of the
     Indenture shall be $0.90 per 100 Units if the greatest number of Units
     outstanding during the period is 10,000,000 or more; $0.96 per 100 Units
     if the greatest number of Units outstanding during the period is between
     5,000,000 and 9,999,999; and $1.00 per 100 Units if the greatest number
     of Units outstanding during the period is 4,999,999 or less.

          L. For a Unit Holder to receive an "in--kind" distribution during the
     life of the Trust, such Unit Holder must tender at least 25,000 Units for
     redemption. There is no minimum amount of Units that a Unit Holder must
     tender in order to receive an "in-kind" distribution on the In-Kind Date or
     in connection with a rollover.

          M. The Indenture is amended to provide that the period during which
     the Trustee shall liquidate the Trust Securities shall not exceed 30
     business days commencing on the first business day following the In-Kind
     Date.

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          (Signatures and acknowledgments on separate pages)

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          The Schedule of Portfolio Securities in the prospectus included in
     this Registration Statement is hereby incorporated by reference herein as
     Schedule A hereto.<PAGE>
                                                                     EXHIBIT 4.1

                                INTERACTIVE DATA
                          FINANCIAL TIMES INFORMATION
                         100 WILLIAM STREET, 15th FLOOR
                            NEW YORK, NEW YORK 10038
                                 (212) 269-6300
                                FAX 212-771-6545

                                                                   July 11, 2001

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<S>                                       <C>
Merrill Lynch, Pierce, Fenner & Smith
Incorporated
Defined Asset Funds
P.O. Box 9051
Princeton, New Jersey 08543-9051

The Bank of New York
101 Barclay Street
New York, New York 10286
</TABLE>

RE: DEFINED ASSET FUNDS--GOVERNMENT SECURITIES INCOME FUND,
    U.S. GOVERNMENT ZERO COUPON SERIES--3 AND 8
(A Unit Investment Trust) Units of Fractional Undivided Interest-Registered
Under the Securities Act of 1933, File Nos. 33-26716 and 333-36109)

Gentlemen:

    We have examined the Registration Statement for the above captioned Fund.

    We hereby consent to the reference to Interactive Data Services, Inc. in the
Prospectus contained in the Post-Effective Amendment No. 12 to the Registration
Statement for the above captioned Fund and to the use of the evaluations of the
Obligations prepared by us which are referred to in such Prospectus and
Registration Statement.

    You are authorized to file copies of this letter with the Securities and
Exchange Commission.

                                          Very truly yours,
                                          STEVEN MIANO
                                          Director Fixed Income
                                          Data Operations

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