Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING PRINCIPLES - Concentration of customer revenues and accounts receivable balance (Details)

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SUMMARY OF SIGNIFICANT ACCOUNTING PRINCIPLES - Concentration of customer revenues and accounts receivable balance (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2018
Jun. 30, 2019
Customer A, related      
Revenue concentration 46.60% 49.10%  
Accounts receivable balance     $ 283,064
Customer B      
Revenue concentration 27.00% 25.60%  
Accounts receivable balance