Note 6 - Warrants (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

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

						Weighted a verage		Aggregate
	Warrants		Exercise			p rice per		intrinsic
As of March 31, 2019 :	o utstanding		p rice per share			share		value (1)
Balance, December 31, 2018		26,872,430	$0.25	–	1.00	$	0.42
Issued		3,861,041	0.16	–	0.25		0.24
Balance, March 31, 2019		30,733,471	$0.16	–	1.00	$	0.40	$	—

As of March 31, 2020 :
Balance, December 31, 2019	43,231,161		$0.16	–	1.00	$	0.35
Issued	791,260				0.13		0.13
Expired	(266,000	)			0.30		0.30
Balance, March 31, 2020	43,756,421		$0.16	–	1.00	$	0.35	$	131,000

Schedule Of Assumptions Used To Determine Fair Value Of Warrants [Table Text Block]

	March 31, 2019			March 31, 2020
Risk free interest rate	2.18	–	2.62%		0.23	%
Expected volatility	86	–	110%		112	%
Expected dividend yield		—			—
Forfeiture rate		—			—
Expected life in years	2	—	5		2