Name	Info	Provider	Link
	subscription/membership/fee required	Ediciones Doyma, S.L.	http://www.elsevier.es/en/linksolver/ft/ivp/0025-7753/130/35
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/13114543
Heroin	free resource	MedlinePlus Health Information	https://medlineplus.gov/heroin.html