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2. STOCK-BASED COMPENSATION (Details 1) (Stock Options, USD $)
3 Months Ended
Aug. 31, 2013
Aug. 31, 2012
Stock Options
   
Expected term (in years) 4 years 5 years
Volatility 95.00% 90.00%
Expected dividend $ 0 $ 0
Risk-free interest rates 1.46% 0.75%
Estimated forfeiture rate 0.25% 0.25%
Weighted average grant date fair value $ 0.92 $ 0.88