Note 3 - Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Level 1		Level 2		Level 3		Total
Liabilities
Liability classified stock purchase warrants	$	-	$	-	$	583,734	$	583,734
Balance at December 31, 2018	$	-	$	-	$	583,734	$	583,734
Liability classified stock purchase warrants	$	-	$	-	$	166,938	$	166,938
Balance at September 30, 2019	$	-	$	-	$	166,938	$	166,938

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

		Mark-to-market liabilities - stock purchase warrants
Balance at December 31, 2018	$	583,734
Change in fair value - gain		(416,796	)
Balance at September 30, 2019	$	166,938

		Mark-to-market liabilities - stock purchase warrants
Balance at December 31, 2017	$	3,852,882
Change in fair value - gain		(1,805,319	)
Balance at September 30, 2018	$	2,047,563