3. Allowance for Doubtful Accounts

12 Months Ended

Dec. 31, 2017

Notes to Financial Statements

3. Allowance for Doubtful Accounts

Changes in the allowance for doubtful accounts are composed of the following:

	Years Ended December 31,
	2017		2016
Balance, beginning of year	$	50	$	49
Provision for doubtful accounts		—		17
Uncollectible accounts written off		—		(16	)
Balance, end of year	$	50	$	50