Name	Info	Provider	Link
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=21359006.ui
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/21359006/
	subscription/membership/fee required	Georg Thieme Verlag Stuttgart, New York	https://www.thieme-connect.com/DOI/DOI?10.1055/s-0030-1254403
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/21359006