Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S0020-6539(20)33148-8
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21995377/
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/21995377
	subscription/membership/fee required	Wiley	https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0020-6539&date=2011&volume=61&issue=5&spage=281
	subscription/membership/fee required	ClinicalKey	https://www.clinicalkey.com/content/playBy/pii?v=S0020-6539(20)33148-8