Name	Info	Provider	Link
	subscription/membership/fee required	Ingenta plc	https://www.ingentaconnect.com/openurl?genre=article&issn=&volume=29&issue=1&spage=76&aulast=BarberÃ
	subscription/membership/fee required	Ovid Technologies, Inc.	http://ovidsp.ovid.com/ovidweb.cgi?T=JS&PAGE=linkout&SEARCH=32134754.ui
	free resource	NCI CPTC Antibody Characterization Program	https://antibodies.cancer.gov/detail/CPTC-CD274-1
	free resource	Biospecimen Research Database	https://brd.nci.nih.gov/brd/paper/appl-immunohistochem-mol-morphol/2020/the-immunohistochemical-expression-of-programmed-death-ligand/132712
	subscription/membership/fee required	Wolters Kluwer	https://doi.org/10.1097/PAI.0000000000000847