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EXHIBIT 4
JOINT FILING AGREEMENT
The undersigned acknowledge and agree that the foregoing statement on
Schedule 13D is filed on behalf of each of the undersigned and that all
subsequent amendments to this statement shall be filed on behalf of each of the
undersigned without the necessity of filing additional joint filing agreements.
The undersigned acknowledge that each shall be responsible for the timely filing
of such amendments, and for the completeness and accuracy of the information
concerning it contained therein, but shall not be responsible for the
completeness and accuracy of the information concerning the others, except to
the extent that it knows or has reason to believe that such information is
inaccurate.
This Agreement may be executed counterparts and each of such counterparts
taken together shall constitute one and the same instrument.
Dated: August 6, 1999
MERCK & CO., INC.
By: /s/ Xxxx X. Xxxxxx
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Name: Xxxx X. Xxxxxx
Title: Senior Vice President and
Chief Financial Officer
MC SUBSIDIARY CORP.
By: /s/ Xxxx X. Xxxxxx
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Name: Xxxx X. Xxxxxx
Title: President
