Quarterly report pursuant to Section 13 or 15(d)

Note 4 - Warrants (Details Textual)

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Note 4 - Warrants (Details Textual) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Aug. 31, 2021
Apr. 30, 2021
Dec. 31, 2020
Share-based Payment Arrangement, Expense $ 977,000 $ 460,000 $ 1,817,000 $ 1,265,000      
Equity Classified Warrants [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) 396,502   396,502   250,000 71,500 109,639
Warrants and Rights Outstanding, Term (Year)         10 years 5 years  
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)         $ 3.08 $ 3.63  
Class of Warrant or Right, Vested and Exercisable (in shares) 182,985   182,985       85,472
Share-based Payment Arrangement, Expense $ 422,000 $ 0 $ 432,000 $ 5,000      
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total $ 632,000   $ 632,000