The following table and related information summarizes the Company’s stock purchase warrants at December 31, 2012 and the stock purchase warrant activity for the three years ended December 31, 2011, 2010 and 2009:
| Number Outstanding |
Weighted-Average Exercise Price per Share |
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Warrants outstanding at December 31, 2009 |
21,067,339 | $ | 2.99 | |||||
|
Expired |
(2,175,243 | ) | 2.93 | |||||
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Warrants outstanding at December 31, 2010 |
18,892,096 | $ | 2.99 | |||||
|
Expired |
(3,299,996 | ) | 2.31 | |||||
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Warrants outstanding at December 31, 2011 |
15,592,100 | $ | 3.14 | |||||
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Expired |
(15,592,100 | ) | 3.14 | |||||
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Warrants outstanding at December 31, 2012 |
— | $ | — | |||||
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