Name	Info	Provider	Link
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=19536648.ui
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/19536648/
	subscription/membership/fee required	Springer	https://doi.org/10.1007/s10484-009-9092-3
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/19536648