s/ MICHAEL ZILKHA ----------------------------------------- Michael Zilkha SELIM K. ZILKHA TRUST

   1
                                                                       EXHIBIT D

         Each of the undersigned hereby agrees that the Amendment No. 1 to
Schedule 13D dated January 30, 1998, to which this Agreement is attached as
Exhibit D, and any amendments thereto, may be filed on behalf of each such
person.

         This Agreement may be executed in any number of counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.


Dated:   February 2, 1998


                                     /s/ XXXXXXX XXXXXX                   
                                     -----------------------------------------
                                     Xxxxxxx Xxxxxx

                                     XXXXX X. XXXXXX TRUST

                                     /s/ XXXXX X. XXXXXX                    
                                     -----------------------------------------
                                     Xxxxx X. Xxxxxx, as Trustee

                                     /s/ XXXXX X. XXXXXX                    
                                     -----------------------------------------
                                     Xxxxx X. Xxxxxx

                                     XXXXX X. XXXXXX (1996) ANNUITY TRUST

                                     /s/ XXXX XXXXXX                          
                                     -----------------------------------------
                                     Xxxx Xxxxxx, as Trustee

                                     /s/ XXXX XXXXXX                          
                                     -----------------------------------------
                                     Xxxx Xxxxxx