TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCE

6 Months Ended

Jun. 30, 2015

TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCE

6. TRADE ACCOUNTS RECEIVABLE, NET OF ALLOWANCE

(in thousands)	June 30, 2015			December 31, 2014
Trade accounts receivable	$	122,210		$	128,757
Unbilled trade accounts receivable		15,127			27,627
Total accounts receivable		137,337			156,384
Allowance for sales credit memos		(1,752	)		(1,540	)
	$	135,585		$	154,844

Unbilled trade accounts receivable primarily relate to services revenue earned under time and materials arrangements and to maintenance and license arrangements which have commenced or been delivered but have not been invoiced.