Name	Info	Provider	Link
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=15030521.ui
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/15030521/
	free resource	Wiley	https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0009-9104&date=2004&volume=136&issue=1&spage=111
	free resource	Silverchair Information Systems	https://academic.oup.com/cei/article-lookup/doi/10.1111/j.1365-2249.2004.02412.x