D. STOCKHOLDERS' EQUITY (Details 5)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Risk-free interest rate (weighted average)		1.83%
Expected volatility (weighted average)		81.26%
Expected term (in years)		1 year 6 months 22 days
Expected dividend yield		0.00%
2016 Plan
Risk-free interest rate (weighted average)	2.85%	0.00%
Expected volatility (weighted average)	102.37%	0.00%
Expected term (in years)	7 years	0 years
Expected dividend yield	0.00%	0.00%
1999 Plan
Risk-free interest rate (weighted average)	2.91%	2.19%
Expected volatility (weighted average)	102.63%	99.59%
Expected term (in years)	7 years	7 years
Expected dividend yield	0.00%	0.00%

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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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 share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

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