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Inventories (Details Textual) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Inventories (Textual)        
Inventory write-down $ 47,977 $ 494,896 $ 457,039 $ 557,668