Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S0196-0644(09)00268-6
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=19380038.ui