Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts receivable, allowance for doubtful accounts	$ 26	$ 0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, issued (in shares)	18,898,609	18,547,406
Common stock, outstanding (in shares)	18,898,609	18,547,406

Amount of allowance for credit loss on accounts receivable, classified as current.

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