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Note 2 - Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2019
Notes Tables  
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]
   
201
9
    
2018
  
                 
Weighted average grant date fair value
   $
3.69
     $
0.49
  
Weighted average assumptions used:
                
Expected dividend yield
    
0.00
%
    
0.00
%
Risk-free interest rate
    
2.00
%
    
0.83
%
Expected volatility
    
124.58
%
    
225.21
%
Expected life (in years)
    
5.00
      
4.91