JOINT FILING AGREEMENT

                                                                  EXHIBIT 48

                             JOINT FILING AGREEMENT

         The undersigned hereby agree to jointly file a statement on Schedule
13D, together with any amendments thereto, with the SEC pursuant to the
requirements of Rule 13d-1(f) under the Securities Exchange Act of 1934, as
amended.

         This Joint Filing Agreement may be signed in counterpart copies.

Date:  Xxxxx 00, 0000                  XXXX Aktiengesellschaft



                                       By:   /s/ Hans Xxxxxxx Xxxx
                                          -----------------------------------
                                          Name:  Dr. Hans Xxxxxxx Xxxx
                                          Title: Chief Financial Officer



                                       By:   /s/ Xxxx Xxxxxx
                                          -----------------------------------
                                          Name:  Xx. Xxxx Xxxxxx
                                          Title: Executive Vice President


Date:  Xxxxx 00, 0000                  XXXX Corporation



                                       By:   /s/ Xxxxx X. Xxxxxxxxx
                                          -----------------------------------
                                          Name:  Xx. Xxxxx X. Xxxxxxxxx
                                          Title: President



                                       By:   /s/ A. Xxxx Xxxxxxxxxxx, Xx.
                                          -----------------------------------
                                          Name:  A. Xxxx Xxxxxxxxxxx, Xx.
                                          Title: Vice President


Date:  March 23, 1999                  VEBA Zweite
                                       Verwaltungsgesellschaft mbH



                                       By:   /s/ Xxxx Xxxxxx
                                          -----------------------------------
                                          Name:  Xx. Xxxx Xxxxxx
                                          Title: Managing Director


                                       By:   /s/ Xxxxx-Xxxxx von der Xxxxx
                                          -----------------------------------
                                          Name:  Xxxxx-Xxxxx von der Xxxxx
                                          Title: Prokurist