8. Warrants

At December 31, 2021 and 2020, the following warrants were outstanding:

​

​

All of the warrant agreements provide for a cashless exercise in the event a registration statement covering the issuance of the shares of common stock underlying the warrants is not effective, whereby the number of shares to be issued upon exercise of such warrants will be reduced based on the exercise price and the market value of the shares at the time of exercise. The outstanding warrants expire from 2022 through 2027.