Note 6 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation expense	$ 191,380	$ 91,204
Research and Development Expense [Member]
Stock-based compensation expense	96,530	13,596
General and Administrative Expense [Member]
Stock-based compensation expense	$ 94,850	$ 77,608

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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