Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Accounts receivable-trade, allowance for doubtful accounts	$ 12,940	$ 15,703
Other intangibles, accumulated amortization	$ 714,000	$ 713,000
Preferred stock, par value (in dollars per share)	$ 0.10	$ 0.10
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0024	$ 0.0024
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	11,348,186	11,346,778
Common stock, shares outstanding (in shares)	8,934,024	9,060,561
Treasury stock, shares (in shares)	2,414,162	2,286,217