International Hospitals – direct sales of products and preservation services.

International Distributors – generally these contracts specify a geographic area that the distributor will service, terms and conditions of the relationship, and purchase targets for the next calendar year.

CardioGenesis Cardiac Laser Console Trials and Sales – CardioGenesis cardiac trialed laser consoles are delivered under separate agreements.

For the three and six months ended June 30, 2019 and 2018 the sources of revenue were as follows (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
		2019		2018		2019		2018
	(Unaudited)				(Unaudited)
Domestic hospitals	$	36,344	$	35,139	$	71,955	$	68,682
International hospitals		22,532		21,902		43,102		40,951
International distributors		10,365		9,877		19,975		17,887
CardioGenesis cardiac laser therapy		1,898		1,578		3,612		2,924
Total sources of revenue	$	71,139	$	68,496	$	138,644	$	130,444

We may generate contract assets during the pre-delivery design and manufacturing stage of E-xtra DESIGN ENGINEERING product order fulfillment. We assess the balance related to any arrangements in process and determine if the enforceable right to payment creates a material contract asset requiring disclosure. No material arrangements in process existed as of June 30, 2019 and 2018.

We also incur contract obligations on general customer purchase orders that have been accepted but unfulfilled. Due to the short duration of time between order acceptance and delivery of the related product or service, we have determined that the balance related to these contract obligations is generally immaterial at any point in time. We monitor the value of orders accepted but unfulfilled at the close of each reporting period to determine if disclosure is appropriate. The value of orders accepted but unfulfilled as of June 30, 2019 and 2018 were not material.