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Accounts Receivable (Details) - USD ($)
Jun. 30, 2018
Dec. 31, 2017
Receivables [Abstract]    
Accounts receivable under normal 30 day terms $ 2,202,296 $ 1,493,084
Financed contracts:    
Current portion of long-term 948,849 1,741,669
Long-term, net of current portion 1,161,112 1,515,120
Total accounts receivable 4,312,257 4,749,873
Less allowance for doubtful accounts (125,027) (181,473)
Accounts receivable, net 4,187,230 4,568,400
Presented on the balance sheet as:    
Accounts receivable, net 3,026,118 3,053,280
Long-term accounts receivable - financed contracts $ 1,161,112 $ 1,515,120