Note 6 - Warrants (Tables)

9 Months Ended

Sep. 30, 2019

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 September 30 , 2018 :	o utstanding			p rice per share				share		value (1)
Balance, December 31, 2017		22,104,817		$	0.125	–	1.00	$	0.45
Issued		6,451,013			0.25	–	0.48		0.23
Expired		(2,683,400	)				0.40		0.40
Balance, September 30, 2018		25,872,430		$	0.125	–	1.00	$	0.39
As of September 30 , 2019 :
Balance, December 31, 2018		26,872,430		$	0.25	–	1.00	$	0.42
Issued		24,321,947			0.10	–	0.30		0.21
Exercised		(7,505,746	)		0.10	–	0.12		0.11
Balance, September 30, 2019		43,688,631		$	0.10	–	1.00	$	0.35	$	1,898,000

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

	September 30 , 2018				September 30 , 2019
Risk free interest rate			2.54	%	1.42	–	2.62	%
Expected volatility			252	%	86	–	110	%
Expected dividend yield		—				—
Forfeiture rate		—				—
Expected life in years	5	–	10		2	—	5