Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/00006396-201112000-00007
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=21889261.ui
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21889261/
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/21889261
	subscription/membership/fee required	Wolters Kluwer	https://doi.org/10.1016/j.pain.2011.08.004