Note 11 - Common Stock (Tables)

9 Months Ended

Sep. 30, 2020

Notes Tables

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

					Shares
					Outstanding
	Exercisable	Expiration	Exercise		Under
Issuance Date	for	Date	Price		Warrants
February 2015	Common Shares	February 17, 2025	$	400.00		754
March 2015	Common Shares	March 26, 2025	$	272.00		14
May 2015	Common Shares	May 12, 2025	$	424.00		362
December 2015	Common Shares	December 16, 2025	$	560.00		267
April 2016	Common Shares	April 1, 2026	$	608.00		250
May 2016	Common Shares	May 11, 2021	$	774.00		50
June 2016	Common Shares	June 20, 2026	$	498.00		1,004
May 2017	Common Shares	May 25, 2027	$	950.00		2,220
November 2019	Common Shares	November 26, 2020	$	0.61		423,809
November 2019	Common Shares	November 26, 2024	$	0.61		3,256,286
November 2019	Common Shares	November 26, 2024	$	1.836		9,893,776
April 2020	Common Shares	April 21, 2025	$	0.6371		4,132,084
						17,710,876

Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

	Immediately		Immediately
	before Modification		After Modification
Exercise price		$1.55		$0.61
Common stock price		$0.63		$0.63
Expected term (in years)		2.8		2.8
Average volatility		97%		97%
Risk-free interest rate		0.27%		0.27%
Dividend yield		0%		0%