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Consolidated Balance Sheets (Parentheticals) - USD ($)
Dec. 31, 2020
Dec. 31, 2019
Accounts receivable, allowance for doubtful accounts $ 498,044 $ 612,434
Inventories, allowance for excess and obsolete inventory 723,949 665,308
Property and equipment, accumulated depreciation 8,908,145 10,815,995
Intangible assets, accumulated depreciations $ 269,441 $ 141,282
Preferred stock, par value (in dollars per share) $ 0.001 $ 0.001
Preferred stock, shares authorized (in shares) 2,500,000 2,500,000
Preferred stock, shares issued (in shares) 0 0
Preferred stock, shares outstanding (in shares) 0 0
Common stock, par value (in dollars per share) $ 0.001 $ 0.001
Common stock, shares authorized (in shares) 25,000,000 25,000,000
Common stock, shares issued (in shares) 21,655,461 20,547,668
Common stock, shares outstanding (in shares) 21,655,461 20,547,668