EXHIBIT A
JOINT FILING AGREEMENT
In accordance with Rule 13d-1(k)(l) under the Securities Exchange Act of 1934,
as amended, the undersigned hereby agree to the joint filing of the attached
Schedule 13G, and any and all amendments thereto, and expressly authorize
AMVESCAP PLC, as the ultimate parent company of each of its undersigned
subsidiaries, to file such Schedule 13G, and any and all amendments thereto, on
behalf of each of them.
Dated: January 23, 2007 AMVESCAP PLC
By: /s/ Xxxx Xxxxxxxx
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Name: Xxxx Xxxxxxxx
Title: Global Compliance Director
AIM Funds Management Inc.
By: /s/ Xxxxx Xxxxxx
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Name: Xxxxx Xxxxxx
Title: Chief Compliance Officer
AIM Private Asset Management, Inc.
By: /s/ Xxxx Xxxxxxxx
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Name: Xxxx Xxxxxxxx
Title: Chief Compliance Officer
Atlantic Trust Company, N.A.
By: /s/ Xxxxx Xxxxxx
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Name: Xxxxx Xxxxxx
Title: General Counsel
Xxxxx Xxx Investment Counsel, Inc.
By: /s/ Xxxx Xxxxxxxx
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Name: Xxxx Xxxxxxxx
Title: General Counsel
PowerShares Capital Management LLC
By: /s/ Xxxxx Xxxxxxxxx
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Name: Xxxxx Xxxxxxxxx
Title: General Counsel & COO
