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Non-marketable equity securities (Tables)
 6 Months Ended
Jun. 30, 2021
Non Marketable Securities [Abstract]  
Schedule of Non-marketable equity securities
   December 31,   June 30, 
   2020   2021 
Cost  $
       -
   $1,393,491 
Impairment   
-
    (691,748)
Carrying amount  $
-
   $701,743