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 6 Months Ended
Jun. 30, 2021
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Dec. 31, 2020
Share-based Payment Arrangement, Expense   $ 433,000 $ 408,000 $ 838,000 $ 805,000  
Warrants Grants During Six Months Ended 2021 [Member]            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) 71,500 71,500   71,500    
Warrants and Rights Outstanding, Term (Year) 5 years 5 years   5 years    
Equity Classified Warrants [Member]            
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) 146,502 146,502   146,502   109,639
Class of Warrant or Right, Vested and Exercisable (in shares) 54,410 54,410   54,410   85,472
Share-based Payment Arrangement, Expense $ 11,000   $ 5,000 $ 11,000 $ 5,000  
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total $ 328,000 $ 328,000   $ 328,000