Note 4 - Stock-based Compensation	6 Months Ended
Oct. 31, 2020
Notes to Financial Statements
Share-based Payment Arrangement [Text Block]	4. STOCK-BASED COMPENSATION During the six months ended October 31, 2020, options to purchase 131,750 shares were granted, options to purchase 29,000 shares were exercised and options to purchase 7,500 shares were cancelled at weighted average exercise prices of $46.94, $13.90 and $5.67 respectively. At October 31, 2020, options to purchase 289,795 shares at a weighted average exercise price of $28.98 per share were outstanding and stock-based awards to purchase 2,676,802 shares of common stock were available for grant.

Note 4 - Stock-based Compensation

6 Months Ended

Oct. 31, 2020

Share-based Payment Arrangement [Text Block]

4. STOCK-BASED COMPENSATION

During the six months ended October 31, 2020, options to purchase 131,750 shares were granted, options to purchase 29,000 shares were exercised and options to purchase 7,500 shares were cancelled at weighted average exercise prices of $46.94, $13.90 and $5.67 respectively. At October 31, 2020, options to purchase 289,795 shares at a weighted average exercise price of $28.98 per share were outstanding and stock-based awards to purchase 2,676,802 shares of common stock were available for grant.