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Note 5 - Intangible Assets (Tables)
3 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Notes Tables    
Schedule of Finite-Lived Intangible Assets [Table Text Block]
   
March 31, 2020
   
December 31, 2019
 
                 
Lighting patent
  $
6,797,000
    $
6,797,000
 
Accumulated amortization
   
(1,522,244
)    
(1,416,041
)
                 
Net
  $
5,274,756
    $
5,380,959
 
   
2019
   
2018
 
                 
Lighting patent
  $
6,797,000
    $
6,797,000
 
Accumulated amortization
   
(1,416,041
)    
(991,229
)
                 
Net
  $
5,380,959
    $
5,805,771