Note 6 - Stockholders' Equity, Stock Options and Warrants (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

Sales of Stock [Table Text Block]

Offering Closing Date	Shares	Sale Price per Share*	Investor Warrants	Exercise Price per Share – Investor Warrants	Placement Agent Warrants	Exercise Price per Share – Placement Agent Warrants	Gross Proceeds of Offering	Net Proceeds of Offering
January 12, 2021 (registered direct)	3,650,840	$0.842	1,825,420	$0.80	273,813	$1.0525	$3,074,007	$2,731,766
January 21, 2021 (registered direct)	2,200,000	$1.00	1,100,000	$1.00	165,000	$1.25	$2,200,000	$1,932,050
January 26, 2021 (registered direct)	3,414,970	$1.20	1,707,485	$1.37	256,123	$1.50	$4,097,964	$3,668,687
February 16, 2021 (registered direct)	4,222,288	$1.75	2,111,144	$2.00	316,672	$2.1875	$7,389,004	$6,679,989
February 23, 2021 (private placement)	9,043,766	$1.95	4,521,883	$2.00	678,282	$2.4375	$17,635,344	$16,064,739
Total	22,531,864		11,265,932		1,689,890		$34,396,319	$31,077,231

Share-based Payment Arrangement, Activity [Table Text Block]

	Stock Options					Warrants
	Number of Shares			Average Exercise Price		Number of Shares			Average Exercise Price
Outstanding at December 31, 2019		766,424		$	11.34		2,171,610		$	15.26
Issued		319,851			1.03		8,097,468			1.547
Forfeited		(72,728	)		10.58		(128,710	)		95.11
Exercised		-			-		(2,786,992	)		0.79
Outstanding at December 31, 2020		1,013,547		$	5.41		7,353,376		$	3.76
Issued		10,680			0.69		12,955,822			1.65
Forfeited		(18,078	)		9.89		-			-
Exercised		-			-		(5,247,059	)		0.86
Outstanding at March 31, 2021		1,006,149		$	5.25		15,062,139		$	2.96