Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S1098-7339(06)00065-4
	subscription/membership/fee required	HighWire	https://rapm.bmj.com/lookup/pmidlookup?view=long&pmid=16857549
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=16857549.ui