Name	Info	Provider	Link
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=21523701.ui
	subscription/membership/fee required	Wiley	https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=&date=2011&volume=98&issue=6&spage=866
	subscription/membership/fee required	Silverchair Information Systems	https://academic.oup.com/bjs/article-lookup/doi/10.1002/bjs.7552