Note 6 - Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Stock-based compensation expense	$ 279,473	$ 145,321	$ 584,297	$ 385,605
Research and Development Expense [Member]
Stock-based compensation expense	19,838	13,519	136,236	40,692
General and Administrative Expense [Member]
Stock-based compensation expense	$ 259,635	$ 131,802	$ 448,061	$ 344,913

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

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