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Note 4 - Intangible Assets (Tables)
 3 Months Ended
Mar. 31, 2021
Notes Tables  
Schedule of Finite-Lived Intangible Assets [Table Text Block]
   
March 31,
2021
    
December 31,
2020
  
                 
Lighting patent
   $
6,797,000
     $
6,797,000
  
Accumulated amortization
    
(1,947,056
 )    
(1,840,853
 )
                 
Net
   $
4,849,944
     $
4,956,147