Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S0271-5317(09)00176-6
Vitamin A	free resource	MedlinePlus Health Information	https://medlineplus.gov/vitamina.html
	free resource	PubMed Central	https://www.ncbi.nlm.nih.gov/pmc/articles/pmid/19917451/
	free resource	Europe PubMed Central	https://europepmc.org/abstract/MED/19917451
	subscription/membership/fee required	ClinicalKey	https://www.clinicalkey.com/content/playBy/pii?v=S0271-5317(09)00176-6