6. LOSS PER SHARE

The following table sets forth the computation of basic and fully diluted loss per common share for the three months ended March 31, 2021 and 2020 (stated in thousands, except per share amounts):

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Basic net loss per share is computed using the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed using the treasury stock method to calculate the weighted average number of common shares and, if dilutive, potential common shares outstanding during the period. Potential dilutive common shares include incremental common shares issuable upon the exercise of stock options, less shares from assumed proceeds. The assumed proceeds calculation includes actual proceeds to be received from the employee upon exercise and the average unrecognized stock compensation cost during the period.

Stock options to purchase 2,638,467 common shares and warrants to purchase 18,325,028 common shares were outstanding at March 31, 2021 that were not included in the computation of diluted weighted average common shares outstanding because their effect would have been anti-dilutive.