Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Accounts receivable, allowance	$ 19,250	$ 19,250
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	10,000,000	10,000,000
Common stock, shares issued (in shares)	4,796,253	4,748,012
Common stock, shares outstanding (in shares)	4,796,253	4,748,012