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Note 6 - Patents (Tables)
 12 Months Ended
Dec. 31, 2019
Notes Tables  
Schedule of Finite-Lived Intangible Assets [Table Text Block]
    2019   2018
Patent asset   $
2,006,443
     $
2,006,443
  
Accumulated amortization    
(1,337,507
 )    
(1,242,900
 )
Net intangibles   $
668,936
     $
763,543