CrossRef is a not-for-profit membership association whose mission is to enable easy identification and use of trustworthy electronic content by promoting the cooperative development and application of a sustainable infrastructure. It is the association behind publishing's preeminent shared digital infrastructure -- a citation linking network that spans tens of millions of resources including journals, books, and other content types. CrossRef is also the official DOI registration agency and provides a variety of valuable services including Cited-by linking, CrossCheck, and CrossRef Metadata Services. Find out more at: www.crossref.org.