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Note 2 - Significant Accounting Policies (Details Textual) - USD ($)	Aug. 02, 2019	Jul. 05, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Retained Earnings (Accumulated Deficit), Ending Balance			$ (93,776,000)		$ (86,361,000)
Cash and Cash Equivalents, at Carrying Value, Ending Balance			517,000		5,358,000	$ 6,834,000	$ 12,689,000
Operating Lease, Right-of-Use Asset			1,292,000	$ 1,505,000
Operating Lease, Liability, Total			$ 1,374,000	$ 1,593,000
Subsequent Event [Member] \| Public Offering [Member]
Proceeds from Issuance or Sale of Equity, Total	$ 8,760,000
Convertible Promissory Note [Member] \| Subsequent Event [Member]
Proceeds from Convertible Debt		$ 625,000