Note 8 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Stock-based compensation expense	$ 515,762	$ 1,221,591
Research and Development Expense [Member]
Stock-based compensation expense	54,155	62,161
General and Administrative Expense [Member]
Stock-based compensation expense	$ 461,607	$ 1,159,430

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

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