Note 7 - Income Taxes - Tax Effects of Significant Temporary Differences Representing Deferred Tax Assets (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Net operating loss carryforwards	$ 43,190,604	$ 42,580,533
Stock based compensation expense	2,605,277	2,643,471
Tax credit carryforwards and other	889,372	1,005,255
Gross deferred tax assets	46,685,253	46,229,259
Valuation allowance	(46,685,253)	(46,229,259)
Net deferred tax assets

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible tax credit carryforwards, classified as other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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