Note 18 - Subsequent Events

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

Subsequent Events [Text Block]

18.

SUBSEQUENT EVENTS

On

February 6, 2018,

we filed a prospectus supplement to the base prospectus that forms a part of the registration statement on Form S-

3

(File

No.

333

-

206789

), filed on

September 4, 2015

and declared effective by the SEC on

September 25, 2015,

pursuant to which we

may

offer and sell up to

$10,000,000

of shares of common stock from time to time under the ATM Agreement. In

January 2018

and thus far in

2018,

we have sold

457,070

shares of common stock for net proceeds of

$1.3

million under the ATM. As of the date of this filing, we have approximately

$12.2

million remaining under the ATM