Joint Filing Agreement

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/ Xxxxx Xxxxxxxxxx
		Name: Xxxxx X. Xxxxxxxxxx
		Title: President
	STERLING PARENT INC.
	By:	/s/ Xxxxx Xxxxxxxxxx
		Name: Xxxxx X. Xxxxxxxxxx
		Title: President
	STERLING MERGER INC.
	By:	/s/ Xxxxx Xxxxxxxxxx
		Name: Xxxxx X. Xxxxxxxxxx
		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/ Xxxx Xxxxx
		Name: Xxxx X. Xxxxx
		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/ Xxxx Xxxxx
		Name: Xxxx X. Xxxxx
		Title: Senior Managing Director
	PROVIDENCE EQUITY GP VI L.P.
	By:	Providence Equity Partners VI L.L.C., its sole general partner
	By:	/s/ Xxxx Xxxxx
		Name: Xxxx X. Xxxxx
		Title: Senior Managing Director
	PROVIDENCE EQUITY PARTNERS VI L.L.C.
	By:	/s/ Xxxx Xxxxx
		Name: Xxxx X. Xxxxx
		Title: Senior Managing Director

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