Exhibit A JOINT FILING UNDERTAKING
Exhibit A
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: September 20, 2007
| Value Fund Advisors, LLC |
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| By: | /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ | |||
| ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇, Manager | ||||
| Boston Avenue Capital, LLC |
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| By: | /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ | |||
| ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇, Manager | ||||
| Yorktown Avenue Capital, LLC |
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| By: | /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ | |||
| ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇, Manager | ||||
| /s/ ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ | ||||
| ▇▇▇▇▇▇▇ ▇. ▇▇▇▇▇▇▇ | ||||