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                                                                EXHIBIT 10.67

                     AMENDMENT NO. 1 TO EMPLOYMENT AGREEMENT

         This Amendment No. 1 (the "Amendment") to the Employment Agreement
dated as of January 1, 1998 (the "Employment Agreement") between Pennsylvania
Real Estate Investment Trust, a Pennsylvania business trust (the "Company"), and
Raymond J. Trost (the "Employee") is hereby entered into as of January 11, 2001
by and between the Company and the Employee. Capitalized terms used but not
otherwise defined herein shall have the meanings ascribed thereto in the
Employment Agreement.

         WHEREAS, the Company and the Employee wish to modify certain provisions
of the Employment Agreement;

         NOW, THEREFORE, in consideration of the mutual covenants contained
herein, and other good and valuable consideration, the parties hereto, intending
to be legally bound, hereby agree to the following amendment to the Employment
Agreement:

         1. Term. Section 3 is hereby amended and restated to read in its
entirety as follows:

                           The term of employment hereunder shall expire on
                           December 31, 2002. Upon the expiration of such
                           period, the term of employment shall be automatically
                           extended for successive terms of two years each,
                           unless either party gives the other not less than one
                           hundred eighty (180) days written notice prior to the
                           expiration of the term of its or his intention not to
                           extend the term of such employment. If such notice is
                           given, the term of employment shall terminate at the
                           end of the then current term.

         2. Entire Agreement. The Employment Agreement, as amended by this
Amendment, constitutes the entire agreement between the parties pertaining to
the subject matter hereof and fully supercedes any and all prior or
contemporaneous agreements or understandings between the parties hereto
pertaining to the subject matter hereof.

         3. Full Force and Effect. Except as expressly amended in this
Amendment, the Employment Agreement shall remain in full force and effect.

         4. Counterparts. This Amendment may be executed in any number of
counterparts, each of which shall be deemed an original, and all of which taken
together shall constitute one and the same agreement.

                                      -7-
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         IN WITNESS WHEREOF, the parties have executed this Amendment as of the
day and year first written above.

                           PENNSYLVANIA REAL ESTATE
                           INVESTMENT TRUST

                           By: /s/ Jonathan B. Weller
                              ---------------------------------------------
                              Name:  Jonathan B. Weller
                              Title:  President and Chief Operating Officer

                           EMPLOYEE

                           /s/ Raymond J. Trost
                           ------------------------------------------------
                           Raymond J. Trost<PAGE>   1

                                                                    EXHIBIT 10.3

     AMENDMENT No. 2, dated as of January 1, 2001, to AMENDED AND RESTATED
MANAGEMENT AGREEMENT, dated as of January 1, 1999, as amended by Amendment No. 1
dated as of January 1, 2000 ("Amendment No. 1") (as so amended, the
"Agreement"), by and among G-I Holdings Inc. (formerly known as GAF Building
Materials Corporation) ("G-I Holdings"), Merick Inc. ("Merick"), International
Specialty Products Inc. (formerly known as ISP Holdings Inc.) ("New ISP"), GAF
Broadcasting Company, Inc. ("Broadcasting"), Building Materials Corporation of
America ("BMCA"), and ISP Opco Holdings Inc. (the "Company"), as assignee of
International Specialty Products Inc. Capitalized terms used and not otherwise
defined herein shall have the meanings ascribed to them in the Agreement.

     WHEREAS, G-I Holdings is the surviving corporation of mergers involving GAF
Corporation, G-I Holdings Inc., G Industries Corp. and GAF Fiberglass
Corporation;

     WHEREAS, in accordance with Section 7 of the Agreement, the parties desire
to (i) adjust the management fees payable to the Company under the Agreement,
effective January 1, 2001, in order to reflect the costs to the Company of
providing services thereunder and (ii) to amend the Agreement to provide that
BMCA shall render management services to G-I Holdings rather than the Company;
and

     WHEREAS, the parties desire to extend the term of the Agreement;

     NOW, THEREFORE, the parties hereby amend the Agreement as follows:

     1.   The definition of "Overhead Group" in the first paragraph of the
Agreement is hereby amended to delete therefrom the references to G-I Holdings,
Merick and Broadcasting.

     2.   Section 1 of the Agreement is hereby amended to (a) extend the term
until March 31, 2001 and (b) to add a proviso before the period at the end of
such section to read in its entirety as follows:

          "; provided that the term of this Agreement shall be automatically
          extended for successive calendar quarters unless a party gives to all
          other parties hereto notice of its intention to terminate no later
          than 30 days prior to the expiration of the then current quarterly
          period."

     3.   Section 2 of the Agreement is hereby amended to add the following
paragraph to the end thereof:

          "BMCA agrees to provide to G-I Holdings, Merick and Broadcasting, to
          the extent required by each of them, management services similar to
          the Services to be provided by the Company to the Overhead Group,
          which shall be provided on a continuous basis without specific
          request. Such services may be changed according to the changing
          business needs of such parties from time to time upon mutual agreement
          by BMCA and G-I Holdings. All services provided by BMCA pursuant to
          this paragraph are herein collectively referred to as "G-I Services."

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     4.   Section 3 of the Agreement is hereby amended to read in its entirety
as follows:

          "In consideration of the Company providing Services hereunder, each of
          the corporations listed below shall pay to the Company a management
          fee (the "Management Fee") at the following respective rates for the
          quarter ending March 31, 2001 and for each quarter thereafter for
          which this Agreement has been extended as provided in Section 1 of
          this Agreement: BMCA (on behalf of itself, its parents and its
          subsidiaries) - $1,358,750 and New ISP - $27,365.75. The Management
          Fee shall be payable quarterly in arrears.

          In addition to the Management Fee, BMCA shall pay to a wholly-owned
          subsidiary of the Company sublease payments pursuant to and in
          accordance with the Sublease between BMCA and such subsidiary, the
          form of which is attached as Exhibit A hereto and made a part hereof.

          The Company, on behalf of its subsidiary as tenant under the Lease
          attached hereto as Exhibit B and made a part hereof (the "Lease),
          shall pay or cause to be paid to the landlord under the Lease (such
          landlord being a subsidiary of G-I Holdings) the lease payments due
          and payable under the Lease in accordance with the terms of the Lease,
          as the Company shall be reimbursed by such subsidiary for all such
          lease payments made on its behalf.

          In consideration of BMCA providing G-I Services hereunder, G-I
          Holdings (on behalf of itself and its subsidiaries other than BMCA and
          BMCA's subsidiaries) shall pay to BMCA a management fee (the "G-I
          Management Fee") at the rate of $152,000 for the quarter ended March
          31, 2001 and for each quarter thereafter for which this Agreement has
          been extended as provided in Section 1 of this Agreement. The G-I
          Management Fee shall be payable quarterly in arrears."

     5.   Section 7(i) of the Agreement is hereby amended to read in its
entirety as follows:

          "(i) The parties acknowledge that the Management Fee and the G-I
          Management Fee have been established to reflect the cost to the
          Company and BMCA, respectively, of providing Services and G-I
          Services, respectively, hereunder on the date hereof. In the event of
          a change of circumstances that materially affects the cost to the
          Company or BMCA, as the case may be, of providing Services and G-I
          Services, respectively, hereunder, including, without limitation, a
          substantial increase in the Services or G-I Services provided by the
          Company or BMCA, respectively, hereunder, the parties shall negotiate
          in good faith such amendments to this Agreement as may be appropriate
          to take into account the effect of any such change of circumstances.
          Such amendments may include, without limitation, an increase or
          decrease of the Management Fee and/or G-I Management Fee."

     6.   Exhibit A to the Agreement is hereby amended to substitute therefor
Exhibit A to this Amendment, and Exhibit B attached to Amendment No. 1 is hereby
ratified and confirmed as Exhibit B to the Agreement.

                                      2
<PAGE>   3

     7.   In all other respects, the Agreement as previously amended shall
remain in full force and effect.

     8.   This Amendment is subject to the approval of the Board of Directors of
the Company.

     9.   This Amendment may be executed in one or more counterparts, each of
which shall be an original but all of which, taken together, shall constitute
one and the same instrument. Failure by any one party to execute this Amendment
shall not effect the rights and obligations of any other party signatory hereto.

     IN WITNESS WHEREOF, the parties have executed this Amendment on the date
and year first above written.

<TABLE>
<S>                                                     <C>
G-I HOLDINGS INC.                                          GAF BROADCASTING COMPANY, INC.

By: /S/ RICHARD A. WEINBERG                                By: /S/ SUSAN B. YOSS
        -------------------------------                        --------------------------------
Name:  Richard A. Weinberg                                 Name:  Susan B. Yoss
Title: President, Chief Executive                          Title: Senior Vice President and Treasurer
       Officer and General Counsel

MERICK INC.                                                BUILDING MATERIALS CORPORATION
                                                                   OF AMERICA
By: /S/ SUSAN B. YOSS                                      By: /S/ WILLIAM W. COLLINS
    -----------------------------------                        --------------------------------
Name:  Susan B. Yoss                                       Name:  William W. Collins
Title: Senior Vice President and Treasurer                 Title: President and
                                                                  Chief Executive Officer

INTERNATIONAL SPECIALTY PRODUCTS INC.                      ISP OPCO HOLDINGS INC.

By: /S/ RANDALL R. LAY                                     By: /S/ RANDALL R. LAY
    -----------------------------------                        --------------------------------
Name:  Randall R. Lay                                      Name:   Randall R. Lay
Title: Executive Vice President and                        Title:  Executive Vice President and
       Chief Financial Officer                                     Chief Financial Officer

</TABLE>

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