EXHIBIT A
The undersigned, Ziff Asset Management, L.P., a Delaware limited
partnership, PBK Holdings, Inc., a Delaware corporation, and Xxxxxx X.
Xxxxxxx, hereby agree and acknowledge that the information required by this
Schedule 13G, to which this Agreement is attached as an exhibit, is filed
on behalf of each of them. The undersigned further agree that any further
amendments or supplements thereto shall also be filed on behalf of each of
them.
Dated: February 3, 2005
ZIFF ASSET MANAGEMENT, L.P.
By: PBK Holdings, Inc., its general
partner
By: /s/ Xxxxx Xxxx
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Name: Xxxxx Xxxx
Title: Vice President
PBK HOLDINGS, INC.
By: /s/ Xxxxx Xxxx
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Name: Xxxxx Xxxx
Title: Vice President
/s/ Xxxxxx X. Xxxxxxx
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Xxxxxx X. Xxxxxxx
