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Common Stock and Stock Purchase Warrants (Details) | 12 Months Ended
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Apr. 30, 2015 | Apr. 30, 2014
Dividend yield | 0.00% | 0.00%
Minimum [Member] |  |
Expected term in years | 1 year 1 month 6 days | 1 year 10 months 24 days
Risk-free interest rates | 0.50% | 0.40%
Volatility | 73.00% | 95.00%
Maximum [Member] |  |
Expected term in years | 4 years 10 months 24 days | 3 years 8 months 12 days
Risk-free interest rates | 1.76% | 1.17%
Volatility | 107.00% | 113.00%

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- Definition Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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