Name	Info	Provider	Link
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=12911087.ui
	subscription/membership/fee required	Silverchair Information Systems	https://research.aota.org/ajot/article-lookup/doi/10.5014/ajot.57.4.450