CUSIP No. 810202101  SCHEDULE 13D

Exhibit A

JOINT FILING UNDERTAKING

The undersigned, being duly authorized thereunto, hereby execute this agreement as an exhibit to this Schedule 13D to evidence the agreement of the below-named parties, in accordance with the rules promulgated pursuant to the Securities Exchange Act of 1934, to file this Schedule jointly on behalf of each such party.

Dated: July 31, 2007

Value Fund Advisors, LLC
By:	/s/ Charles M. Gillman Charles M. Gillman, Manager
Boston Avenue Capital, LLC
By:	/s/ Charles M. Gillman Charles M. Gillman, Manager
Yorktown Avenue Capital, LLC
By:	/s/ Charles M. Gillman Charles M. Gillman, Manager
/s/ Charles M. Gillman
Charles M. Gillman