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BALANCE SHEETS (Parenthetical) - USD ($)
Dec. 31, 2020
Dec. 31, 2019
Accounts receivable, allowance for doubtful accounts (in dollars) $ 205,822 $ 146,832
Common stock, par value (in dollars per share) $ 0 $ 0
Common Stock, authorized shares 100,000,000 100,000,000
Common Stock, outstanding shares 33,957,204 32,674,954
Preferred Class B    
Preferred stock, par value (in dollars per share) $ 1.00  
Preferred Stock, Shares Authorized 5,000,000 5,000,000
Series I, Class B    
Preferred stock, par value (in dollars per share) $ 1  
Preferred Stock, outstanding shares 0 96,000
Series II, Class B    
Preferred stock, par value (in dollars per share) $ 1 $ 1
Preferred Stock, outstanding shares 156,200 171,200
Preferred Stock, liquidation preference (in dollars) $ 1,952,500  
Series III Preferred Stock    
Preferred stock, par value (in dollars per share) $ 1 $ 1
Preferred Stock, outstanding shares 106,745 129,245
Preferred Stock, liquidation preference (in dollars) $ 1,334,313  
Series IV Preferred Stock    
Preferred stock, par value (in dollars per share) $ 1 $ 1
Preferred Stock, outstanding shares 0 342,500
Series V Preferred Stock    
Preferred stock, par value (in dollars per share) $ 1 $ 1
Preferred Stock, outstanding shares 0 34,000