Quarterly report pursuant to Section 13 or 15(d)

Note 4 - Warrants - Warrants Outstanding (Details)

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Note 4 - Warrants - Warrants Outstanding (Details) - $ / shares
9 Months Ended 12 Months Ended
Sep. 30, 2020
Dec. 31, 2019
Feb. 10, 2020
Balance outstanding (in shares) 17,009,495 10,763,995  
Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) $ 1.63    
Warrants Issued in February 2017 [Member]      
Balance outstanding (in shares) [1] 404,002 404,002  
Balance outstanding, remaining contractual life (Year) [1] 1 year 4 months 24 days    
Warrants Issued in February 2017 [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) [1] $ 1.50    
Warrants Issued in February 2018 [Member]      
Balance outstanding (in shares) [1] 2,273,700 2,273,700  
Balance outstanding, remaining contractual life (Year) [1] 2 years 10 months 24 days    
Warrants Issued in February 2018 [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) [1] $ 2.80    
Warrants Issued in June 2018 [Member]      
Balance outstanding (in shares) [1],[2] 742,991 742,991  
Balance outstanding, remaining contractual life (Year) [1],[2] 3 years 2 months 12 days    
Warrants Issued in June 2018 [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) [1],[2] $ 2.03    
Warrants Issued in March 2019 [Member]      
Balance outstanding (in shares) [1] 1,581,000 1,585,500  
Balance outstanding, remaining contractual life (Year) [1] 3 years 6 months    
Warrants Issued in March 2019 [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) [1] $ 1.10    
Warrants Issued in April 2019 [Member]      
Balance outstanding (in shares) [1] 5,250,000 5,250,000  
Balance outstanding, remaining contractual life (Year) [1] 3 years 7 months 6 days    
Warrants Issued in April 2019 [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) [1] $ 1.75    
Warrants Issued in Connection with the February 2020 Stock Offering [Member]      
Balance outstanding (in shares) [1] 6,150,000 0  
Balance outstanding, warrant exercise price (in dollars per share)     $ 1.05
Balance outstanding, remaining contractual life (Year) [1] 4 years 9 months 18 days    
Warrants Issued in Connection with the February 2020 Stock Offering [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) [1] $ 1.05    
Liability Classified Warrants [Member]      
Balance outstanding (in shares) [1] 16,401,693 10,256,193  
Balance outstanding, remaining contractual life (Year) 3 years 10 months 24 days 4 years  
Liability Classified Warrants [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) $ 1.58 [1] $ 1.89  
Warrants Issued in May 2016 to Bonwick [Member]      
Balance outstanding (in shares) 107,802 107,802  
Balance outstanding, remaining contractual life (Year) 7 months 6 days    
Warrants Issued in May 2016 to Bonwick [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) $ 7.50    
Warrants Issued in July 2017 for Consulting [Member]      
Balance outstanding (in shares) [3] 150,000 150,000  
Balance outstanding, remaining contractual life (Year) [3] 1 year 9 months 18 days    
Warrants Issued in July 2017 for Consulting [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) [3] $ 2.61    
Warrants Issued in April 2018 for Consulting [Member]      
Balance outstanding (in shares) 100,000 100,000  
Balance outstanding, remaining contractual life (Year) 6 months    
Warrants Issued in April 2018 for Consulting [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) $ 3.00    
Warrants Issued in August 2019 for Consulting [Member]      
Balance outstanding (in shares) 150,000 150,000  
Balance outstanding, remaining contractual life (Year) 1 year 10 months 24 days    
Warrants Issued in August 2019 for Consulting [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) $ 1.64    
Warrants Issued in April 2020 for Consulting [Member]      
Balance outstanding (in shares) 100,000 0  
Balance outstanding, remaining contractual life (Year) 4 years 7 months 6 days    
Warrants Issued in April 2020 for Consulting [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) $ 1.14    
Equity Classified Warrants [Member]      
Balance outstanding (in shares) 607,802 507,802  
Equity Classified Warrants [Member] | Weighted Average [Member]      
Balance outstanding, warrant exercise price (in dollars per share) $ 3.06    
[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.
[2] Includes warrants to purchase 710,212 shares at an exercise price of $2.02, expiring December 22, 2023, and warrants to purchase 32,779 shares at an exercise price of $2.32, expiring June 21, 2023.
[3] Includes warrants to purchase 100,000 shares at an exercise price of $2.41 and warrants to purchase 50,000 shares at an exercise price of $3.00.