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2. ACCOUNTS RECEIVABLE, NET (Tables)
 12 Months Ended
Dec. 31, 2018
Accounts Receivable, after Allowance for Credit Loss [Abstract]  
Changes in the allowance for doubtful accounts
    Year ended December 31,  
    2018     2017  
             
Balance at Beginning of Period   $ 3,977     $ 15,921  
Charged to costs and expenses     4,618       -  
Charged to other accounts     -       -  
Write-offs, net of recoveries     (1,497 )     (11,944 )
                 
Balance at End of Period   $ 7,098     $ 3,977