Note 7 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-based compensation expense	$ 327,396	$ 292,501	$ 971,832	$ 973,950
Research and Development Expense [Member]
Stock-based compensation expense	16,202	14,333	48,848	81,737
General and Administrative Expense [Member]
Stock-based compensation expense	$ 311,194	$ 278,168	$ 922,984	$ 892,213

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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