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
Feb. 10, 2020
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Apr. 30, 2020
Dec. 31, 2019
Class of Warrant or Right, Outstanding (in shares)   17,009,495   17,009,495     10,763,995
Share-based Payment Arrangement, Expense   $ 460,000 $ 489,000 $ 1,265,000 $ 1,155,000    
Warrants Issued in June 2018 and Expiring December 22, 2023 [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)   710,212   710,212      
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)   $ 2.02   $ 2.02      
Warrants Issued in June 2018 and Expiring June 21, 2023 [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)   32,779   32,779      
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)   $ 2.32   $ 2.32      
Warrants Issued in July 2017 for Consulting with Exercise Price of 2.41 [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)   100,000   100,000      
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)   $ 2.41   $ 2.41      
Warrants Issued in July 2017 for Consulting with Exercise Price 3.00 [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)   50,000   50,000      
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)   $ 3.00   $ 3.00      
Warrants Issued in Connection with the February 2020 Stock Offering [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) 5,625,000            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) $ 1.05            
Class of Warrant or Right, Initial Exercise Period (Month) 6 months            
Warrants and Rights Outstanding, Term (Year) 5 years            
Class of Warrant or Right, Outstanding (in shares) [1]   6,150,000   6,150,000     0
Oppenheimer Co, Underwriter Warrant [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) 525,000            
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) $ 1.05            
Warrants Issued in April 2020 for Consulting [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)           100,000  
Class of Warrant or Right, Vesting Contingency, Research and Development Expenditures Threshold           $ 10,000,000  
Class of Warrant or Right, Outstanding (in shares)   100,000   100,000     0
Equity Classified Warrants [Member]              
Class of Warrant or Right, Outstanding (in shares)   607,802   607,802     507,802
Class of Warrant or Right, Vested and Exercisable (in shares)   512,802   512,802     507,802
Share-based Payment Arrangement, Expense   $ 0 $ 92,000 $ 5,000 $ 94,000    
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total   $ 91,000   $ 91,000      
[1] If the Company subdivides (by any stock split, stock dividend, recapitalization or otherwise) its outstanding shares of its common stock into a smaller number of shares, the warrant exercise price is proportionately reduced and the number of shares under outstanding warrants is proportionately increased. Additionally, if the Company combines (by combination, reverse stock split or otherwise) its outstanding shares of common stock into a smaller number of shares, the warrant exercise price is proportionately increased and the number of shares under outstanding warrants is proportionately decreased. Also, the Company may voluntarily reduce the warrant exercise price for its warrants issued in March 2019 and February 2017 and may voluntarily extend the contractual term of its warrants issued in February 2017.