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 months ended March 31, 2020 and 2019 the sources of revenue were as follows (in thousands):


	Three Months Ended
	March 31,
		2020		2019
	(Unaudited)
Domestic hospitals	$	36,336	$	35,611
International hospitals		19,737		20,570
International distributors		10,245		9,610
CardioGenesis cardiac laser therapy		111		1,714
Total sources of revenue	$	66,429	$	67,505

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 March 31, 2020 and 2019.

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 March 31, 2020 and 2019 was not material.