Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S1098-7339(07)00004-1
	subscription/membership/fee required	HighWire	https://rapm.bmj.com/lookup/pmidlookup?view=long&pmid=17350529
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=17350529.ui