Name	Info	Provider	Link
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=16187208.ui
	subscription/membership/fee required	Springer	https://www.springerlink.com/openurl.asp?genre=article&issn=0364-3190&volume=30&issue=6-7&spage=713