Note 7 - Stockholders' Equity - Black-scholes Valuation Assumptions for Options (Details) - Share-based Payment Arrangement, Option [Member]	9 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Volatility
Dividend yield
Risk-free interest rate
Expected term (Year)
Weighted Average [Member]
Volatility	69.00%	74.00%
Risk-free interest rate	2.71%	2.44%
Expected term (Year)	3 years 292 days	5 years
Minimum [Member]
Volatility	58.00%	68.00%
Risk-free interest rate	2.52%	1.75%
Expected term (Year)	1 year 328 days	3 years
Maximum [Member]
Volatility	76.00%	75.00%
Risk-free interest rate	2.78%	2.64%
Expected term (Year)	4 years 109 days	6 years

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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