Quarterly report pursuant to Section 13 or 15(d)

Note 4 - Stockholders' Equity - Stock Options by Exercise Price Range (Details)

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Note 4 - Stockholders' Equity - Stock Options by Exercise Price Range (Details) - USD ($)
9 Months Ended 12 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Number of options outstanding (in shares) 299,730  
Weighted- average exercise price (in dollars per share) $ 61.78 $ 215.60
Weighted- average remaining contractual life (Year) 7 years 328 days 5 years 36 days
Aggregate intrinsic value  
Range One [Member]    
Range of exercise prices, lower limit (in dollars per share) $ 5.90  
Range of exercise prices, upper limit (in dollars per share) $ 6  
Number of options outstanding (in shares) 58,010  
Weighted- average exercise price (in dollars per share) $ 5.99  
Weighted- average remaining contractual life (Year) 9 years 109 days  
Aggregate intrinsic value  
Range Two [Member]    
Range of exercise prices, lower limit (in dollars per share) $ 7.20  
Range of exercise prices, upper limit (in dollars per share) $ 8.80  
Number of options outstanding (in shares) 162,593  
Weighted- average exercise price (in dollars per share) $ 8.51  
Weighted- average remaining contractual life (Year) 9 years 73 days  
Aggregate intrinsic value  
Range Three [Member]    
Range of exercise prices, lower limit (in dollars per share) $ 22.20  
Range of exercise prices, upper limit (in dollars per share) $ 99.20  
Number of options outstanding (in shares) 36,138  
Weighted- average exercise price (in dollars per share) $ 33.20  
Weighted- average remaining contractual life (Year) 5 years 219 days  
Aggregate intrinsic value  
Range Four [Member]    
Range of exercise prices, lower limit (in dollars per share) $ 107.40  
Range of exercise prices, upper limit (in dollars per share) $ 1,102.41  
Number of options outstanding (in shares) 42,989  
Weighted- average exercise price (in dollars per share) $ 362.61  
Weighted- average remaining contractual life (Year) 2 years 328 days  
Aggregate intrinsic value