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Trade Accounts and Bills Receivable, net (Tables)
3 Months Ended
Mar. 31, 2021
Trade Accounts And Bills Receivable Net [Abstract]  
Schedule of trade accounts and bills receivable
   December 31,   March 31, 
   2020   2021 
Trade accounts receivable  $33,305,997   $27,621,392 
Less: Allowance for doubtful accounts   (5,266,828)   (5,094,948)
    28,039,169    22,526,444 
Bills receivable   1,532,105    780,226 
   $29,571,274   $23,306,670 
Schedule of analysis of the allowance for doubtful accounts
   March 31,   March 31, 
   2020   2021 
Balance at beginning of period  $4,650,686   $5,266,828 
Provision for the period   871,483    - 
Reversal – recoveries by cash   (198,297)   (154,061)
Charged to consolidated statements of operations and comprehensive income (loss)   673,186    (154,061)
Foreign exchange adjustment   (86,308)   (17,819)
Balance at end of period  $5,237,564   $5,094,948