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Note 7 - Patents (Details Textual) - USD ($)
3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Amortization of Intangible Assets, Total     $ 39,760 $ 801,426  
Impairment of Intangible Assets, Finite-lived $ 1,539,794 1,539,794 $ 1,500,000
Patents [Member]          
Amortization of Intangible Assets, Total $ 13,000 $ 332,000 $ 40,000 $ 801,000  
Patents [Member] | Minimum [Member]          
Finite-Lived Intangible Asset, Useful Life     3 years    
Patents [Member] | Maximum [Member]          
Finite-Lived Intangible Asset, Useful Life     20 years