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Share-Based Payments (Details 1)
12 Months Ended
Apr. 30, 2015
Apr. 30, 2014
Risk-free interest rates Minimum 0.80% 0.70%
Risk-free interest rates Maximum 1.90% 2.40%
Volatility Minimum 86.00% 84.00%
Volatility Maximum 102.00% 102.00%
Dividend yield 0.00% 0.00%
Minimum [Member]    
Expected term in years 2 years 6 months 3 years
Maximum [Member]    
Expected term in years 6 years 6 years