Consolidated Condensed Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Jan. 31, 2024	Apr. 30, 2023
Short term investments	$ 4,739	$ 7,240
Allowance for doubtful accounts	$ 33	$ 36
Common stock, par value (in dollars per share)	$ 0.1	$ 0.1
Common stock, shares authorized (in shares)	30,000,000	30,000,000
Common stock, shares issued (in shares)	10,000,000	10,000,000
Treasury stock, shares (in shares)	573,017	565,460