CrossRef is a not-for-profit network founded on publisher collaboration, with a mandate to make reference linking throughout online scholarly literature efficient and reliable. As such, it is an infrastructure for linking citations across publishers, and
Free DOI look-ups via Simple Text Query. Enter whole bibliographies/citations in almost any format, receive back Digital Object Identifiers (DOIs). Retrieve DOIs for all types of pubs in any citation style. DOIs provide persistent links to pubs.