Name	Info	Provider	Link
	subscription/membership/fee required	Elsevier Science	https://linkinghub.elsevier.com/retrieve/pii/S0039-6257(07)00057-4
Tears	free resource	MedlinePlus Health Information	https://medlineplus.gov/tears.html
Cited by Patents in	free resource	The Lens - Patent Citations	https://www.lens.org/lens/search/patent/list?q=citation_id:17574063