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ACCOUNTS RECEIVABLE
12 Months Ended
Dec. 31, 2018
Receivables [Abstract]  
ACCOUNTS RECEIVABLE

5.    ACCOUNTS RECEIVABLE

 

Accounts receivable consists of trade receivables as follows:

 

   December 31, 
   2018   2017 
         
Billed receivables  $8,898,329   $5,529,821 
Less: allowance for doubtful accounts   (275,000)   (150,000)
   $8,623,329   $5,379,821