Note 9 - Stock-based Compensation - Allocation of Stock Option Expense (Details) - Employee Stock Option [Member] - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allocated stock option expense	$ 155,304	$ 57,224	$ 54,805
General and Administrative Expense [Member]
Allocated stock option expense	113,306	31,271	31,191
Research and Development Expense [Member]
Allocated stock option expense	$ 41,998	$ 25,953	$ 23,614

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
-Topic 718
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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