EXHIBIT 3

JOINT FILING AGREEMENT

The undersigned hereby agree to the joint filing of the Amendment No. 4 to Schedule 13D to which this Agreement is attached.

Dated:  July 9, 2008

DISCOVERY GROUP I, LLC
for itself and as general partner of
DISCOVERY EQUITY PARTNERS, L.P.
By	Michael R. Murphy*
	Michael R. Murphy
	Managing Member
Daniel J. Donoghue*
Daniel J. Donoghue
Michael R. Murphy*
Michael R. Murphy
*By:		/s/ Marck Buckley
		Mark Buckley
		Attorney-in-Fact for Daniel J. Donoghue
		Attorney-in-Fact for Michael R. Murphy