Exhibit 7.1

Joint Filing Agreement

Pursuant to Rule 13d-1(k)(1) promulgated under the Securities Exchange Act of 1934, as amended, the undersigned agree that the Statement on Schedule 13D to which this exhibit is attached is filed on behalf of each of them in the capacities set forth below.

Dated:  April 8, 2011

STERLING HOLDCO INC.
By:	/s/ Julie Richardson
	Name: Julie G. Richardson
	Title: President
STERLING PARENT INC.
By:	/s/ Julie Richardson
	Name: Julie G. Richardson
	Title: President
STERLING MERGER INC.
By:	/s/ Julie Richardson
	Name: Julie G. Richardson
	Title: President

PROVIDENCE EQUITY PARTNERS VI L.P.
By:	Providence Equity GP VI L.P., its sole general partner
By:	Providence Equity Partners VI L.L.C., its sole general partner
By:	/s/ Paul Salem
	Name: Paul J. Salem
	Title: Senior Managing Director
PROVIDENCE EQUITY PARTNERS VI-A L.P.
By:	Providence Equity GP VI L.P., its sole general partner
By:	Providence Equity Partners VI L.L.C., its sole general partner
By:	/s/ Paul Salem
	Name: Paul J. Salem
	Title: Senior Managing Director
PROVIDENCE EQUITY GP VI L.P.
By:	Providence Equity Partners VI L.L.C., its sole general partner
By:	/s/ Paul Salem
	Name: Paul J. Salem
	Title: Senior Managing Director
PROVIDENCE EQUITY PARTNERS VI L.L.C.
By:	/s/ Paul Salem
	Name: Paul J. Salem
	Title: Senior Managing Director

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