Name	Info	Provider	Link
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/20039140/
	subscription/membership/fee required	Springer	https://dx.doi.org/10.1007/s11524-009-9397-9
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/20039140