CrossRef DOI Resolver API - SDKs

CrossRef is the "citation linking backbone for all scholarly information in electronic form." CrossRef provides a DOI (Digital Object Identifier) resolver service, as well as an API for this service. Queries can be made with bibliographic data to retrieve a DOI, or a DOI can be provided to retrieve associated metadata. HTTP GET and XML are used for queries and responses are returned in pipe delimited, XSD_XML, or unixref formats.