<PAGE>


                MORGAN STANLEY DEAN WITTER SELECT EQUITY TRUST
                      SELECT 10 INDUSTRIAL PORTFOLIO 2001-2
                            REFERENCE TRUST AGREEMENT


             This Reference Trust Agreement dated February 28, 2001
between DEAN WITTER REYNOLDS INC., as Depositor, and The Bank of New
York, as Trustee, sets forth certain provisions in full and incorporates
other provisions by reference to the document entitled "Morgan Stanley
Dean Witter Select Equity Trust, Trust Indenture and Agreement" (the
"Basic Agreement") dated September 30, 1993 as amended on December 30,
1997. 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 as
follows:

          A.  The first sentence of Section 2.01 is amended to add the
     following language at the end of such sentence: "and/or cash (or a letter
     of credit in lieu of cash) with instructions to the Trustee to purchase
     one or more of such Securities which cash (or cash in an amount equal to
     the face amount of the letter of credit), to the extent not used by the
     Trustee to purchase such Securities within the 90-day period following
     the first deposit of Securities in the Trust, shall be distributed to
     Unit Holders on the Distribution Date next following such 90-day period
     or such earlier date as the Depositor and the Trustee determine".

<PAGE>

                                       -2-

          B.  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.

          C.  The first sentence of Section 2.06 is amended to add the
     following language after "Securities"))": "and/or cash (or a letter of
     credit in lieu of cash) with instructions to the Trustee to purchase one
     or more Additional Securities which cash (or cash in an amount equal to
     the face amount of the letter of credit), to the extent not used by the
     Trustee to purchase such Additional Securities within the 90-day period
     following the first deposit of Securities in the Trust, shall be
     distributed to Unit Holders on the Distribution Date next following such
     90-day period or such earlier date as the Depositor and the Trustee
     determine".

          D.  Article III, entitled "Administration of Trust", Section 3.01
     Initial Cost shall be amended as follows:

              Section 3.01 Initial Cost shall be amended to substitute
the following language:

              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 di-

<PAGE>

                                       -3-

     rected 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 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.

          E.  The third paragraph of Section 3.05 is hereby amended to add
     the following sentence after the first sentence thereof: "Depositor may
     direct the Trustee to invest the proceeds of any sale of Securities not
     required for the redemption of Units in eligible money market instruments
     selected by the Depositor which will include only negotiable certificates
     of deposit or time deposits of domestic banks which are members of the
     Federal Deposit Insurance Corporation and which have, together with their
     branches or subsidiaries, more than $2 billion in total assets, except
     that certificates of deposit or time deposits of smaller domestic banks
     may be held provided the deposit does not exceed the insurance coverage
     on the instrument (which currently is $100,000), and provided further
     that the Trust's aggregate holding of certificates of deposit or time
     deposits issued by the Trustee may not ex-

<PAGE>

                                       -4-

     ceed the insurance coverage of such obligations and U.S. Treasury notes
     or bills (which shall be held until the maturity thereof) each of which
     matures prior to the  earlier of the next following Distribution Date or
     90 days after receipt, the principal thereof and interest thereon (to the
     extent such interest is not used to pay Trust expenses) to be distributed
     on the earlier of the 90th day after receipt or the next following
     Distribution Date."

          F.  The first sentence of each of Sections 3.10, 3.11 and 3.12 is
     amended to insert the following language at the beginning of such
     sentence, "Except as otherwise provided in Section 3.13,".

          G.  The following new Section 3.13 is added

          Section 3.13. EXTRAORDINARY EVENT-SECURITY RETENTION AND VOTING.
     In the event the Trustee is notified of any action to be taken or
     proposed to be taken by holders of the securities held by the Trust in
     connection with any proposed merger, reorganization, spin-off, split-off
     or split-up by the issuer of stock or securities held in the Trust, the
     Trustee shall take such action or refrain from taking any action, as
     appropriate, so as to insure that the securities are voted as closely as
     possible in the same manner and in the same general proportion as are the
     securities held by owners other than the Trust. If stock or securities
     are received by the Trustee, with or without cash, as a result of any
     merger, reorganization, spin-off, split-off or split-up by the issuer of
     stock or securities held in the Trust, the Trustee at the direction of
     the Depositor may retain such stock or securities in the Trust. Neither
     the Depositor nor the Trustee shall be liable to any person for any
     action or failure to take action with respect to this section.

          H.  Section 1.01 is amended to add the following definition:
     (9) "Deferred Sales Charge" shall mean any deferred sales charge payable
     in accordance with the provisions of Section 3.14 hereof, as set forth in
     the prospectus for a Trust.  Definitions following this definition (9)
     shall be renumbered.

          I.  Section 3.05 is hereby amended to add the following paragraph
     after the end thereof: On each Deferred Sales Charge payment date set
     forth in the prospectus for

<PAGE>

                                       -5-

     a Trust, the Trustee shall pay the account created pursuant to Section
     3.14 the amount of the Deferred Sales Charge payable on each such date as
     stated in the prospectus for a Trust. Such amount shall be withdrawn from
     the Principal Account from the amounts therein designated for such
     purpose.

          J.  Section 3.06B(3) shall be amended by adding the following:  "and
     any Deferred Sales Charge paid".

          K.  Section 3.08 shall be amended by adding the following at the end
     thereof: "In order to pay the Deferred Sales Charge, the Trustee shall
     sell or liquidate an amount of Securities at such time and from time to
     time and in such manner as the Depositor shall direct such that the
     proceeds of such sale or liquidation shall equal the amount required to
     be paid to the Depositor pursuant to the Deferred Sales Charge program as
     set forth in the prospectus for a Trust.

          L.  Section 3.14 shall be added as follows:

          Section 3.14. Deferred Sales Charge. If the prospectus for a Trust
     specifies a Deferred Sales Charge, the Trustee shall, on the dates
     specified in and as permitted by the prospectus, withdraw from the Income
     Account if such account is designated in the prospectus as the source of
     the payments of the Deferred Sales Charge, or to the extent funds are not
     available in that account or if such account is not so designated, from
     the Principal Account, an amount per Unit specified in the prospectus and
     credit such amount to a special, non-Trust account maintained at the
     Trustee out of which the Deferred Sales Charge will be distributed to the
     Depositor. If the Income Account is not designated as the source of the
     Deferred Sales Charge payment or if the balances in the Income and
     Principal Accounts are insufficient to make any such withdrawal, the
     Trustee shall, as directed by the Depositor, either advance funds, if so
     agreed to by the Trustee, in an amount equal to the proposed withdrawal
     and be entitled to reimbursement of such advance upon the deposit of
     additional monies in the Income Account or the Principal Account, sell
     Securities and credit the proceeds thereof to such special Depositor's
     account or credit Securities in kind to such special Depositor's Account.
     Such directions shall identify the Securities, if any, to be

<PAGE>

                                       -6-

     sold or distributed in kind and shall contain, if the Trustee is directed
     by the Depositor to sell a Security, instructions as to execution of such
     sales. If a Unit Holder redeems Units prior to full payment of the
     Deferred Sales Charge, the Trustee shall, if so provided in the
     prospectus, on the Redemption Date, withhold from the Redemption Price
     payment to such Unit Holder an amount equal to the unpaid portion of the
     Deferred Sales Charge and distribute such amount to such special
     Depositor's account or, if the Depositor shall purchase such Unit
     pursuant to the terms of Section 5.02 hereof, the Depositor shall pay the
     Redemption Price for such Unit less the unpaid portion of the Deferred
     Sales Charge. The Depositor may at any time instruct the Trustee to
     distribute to the Depositor cash or Securities previously credited to the
     special Depositor's account.

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


                                       II.

                     SPECIAL TERMS AND CONDITIONS OF TRUST


          The following special terms and conditions are hereby agreed to:

          A.  The Trust is denominated Morgan Stanley Dean Witter Select
Equity Trust Select 10 Industrial Portfolio 2001-2 (the "Select 10 Trust").

          B.  The publicly traded stocks listed in Schedule A hereto are
those which, subject to the terms of this Indenture, have been or are to be
deposited in trust under this Indenture.

          C.  The term "Depositor" shall mean Dean Witter Reynolds Inc.

          D.  The aggregate number of Units referred to in Sections 2.03 and
9.01 of the Basic Agreement is 25,014 for the Select 10 Trust.

          E.  A Unit is hereby declared initially equal to 1/25,014th for the
Select 10 Trust.

<PAGE>

                                       -7-

          F.  The term "In-Kind Distribution Date" shall mean April 11, 2002.

          G.  The term "Record Dates" shall mean October 1, 2001, January 1,
2002 and May 1, 2002 and such other date as the Depositor may direct.

          H.  The term "Distribution Dates shall mean October 15, 2001,
January 15, 2002 and on or about May 8, 2002 and such other date as the
Depositor may direct.

          I.  The term "Termination Date" shall mean May 1, 2002.

          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 $0.72 per 100 Units.

          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 14
business days commencing on the first business day following the In-Kind Date.

             (Signatures and acknowledgments on separate pages)

<PAGE>

                                       -8-

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