Name	Info	Provider	Link
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=30422236.ui
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/30422236/
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/30422236
	subscription/membership/fee required	Silverchair Information Systems	https://jamanetwork.com/journals/jamasurgery/fullarticle/10.1001/jamasurg.2018.3861