Please respond to SPARC with requests for documents or more information, as well as additions or corrections to the following lists. Contact companies individually for product pricing.
CrossRef is the citation linking backbone---a collaborative reference linking service that allows the user to click on a citation and be taken directly to the target content. Operated by the Publishers International Linking Association, CrossRef is a non-profit corporation working to facilitate automated reference linking across publishers. Their technology is based on Digital Object Identifiers (DOIs).
Link Openly, Openly Informatics
Link Openly is based on the open S-Link-S specifications which use internet standard XML and RDF syntax to provide reference linking. Registration templates help the linkees (publishers of online scholarly texts) which complement templates and databases for linkers (librarians and publishers). Openly Informatics provides full source code to all licensed users and publishes all the specs of its open linking standard.
Contact: Openly Informatics