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Redeemable Common Stock and Stock Purchase Warrants (Details)
12 Months Ended
Apr. 30, 2013
Apr. 30, 2012
Dividend yield 0.00% 0.00%
Warrant [Member]
   
Expected term in years   3 years 10 months 24 days
Risk-free interest rates 0.30% 0.60%
Volatility   102.00%
Dividend yield 0.00% 0.00%
Warrant [Member] | Minimum [Member]
   
Expected term in years 2 years 10 months 24 days  
Volatility 95.00%  
Warrant [Member] | Maximum [Member]
   
Expected term in years 4 years 8 months 12 days  
Volatility 98.00%