Name	Info	Provider	Link
	free resource	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S0092-8674(22)01545-8
Opioid receptors - overview and references	free resource	Guide to Pharmacology	https://www.guidetopharmacology.org/GRAC/FamilyDisplayForward?familyId=50