We are proud to announce that COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations, has just been extended with more than 31 million additional citations.
As introduced in an earlier blog post and an open-access article recently published on Scientometrics, COCI is our first OpenCitations Index of open citations. In COCI, we have applied the concept of citations as first-class data entities, each identified using a unique persistent Open Citation Identifier (OCI). COCI indexes the contents of one of the major databases of open scholarly citation information, namely Crossref, and renders and makes available this information in machine-readable RDF and in other formats.
The fourth release of COCI contains more than 655 million DOI-to-DOI citation links between more than 55 million bibliographic entities. The additional 31 million citations added in the new release come from the reprocessing of previous dumps of Crossref data. In particular, we retrieved all the citations that involve references in citing articles that were in the Crossref ‘Limited’ set when we downloaded it in October 2018. Such citing articles currently appear in the Crossref ‘Closed’ dataset due to more recent restrictive policy decisions taken by their publishers.
Finally, we wish to remind you that all the bibliographic and citation data in COCI:
- can be queried using the COCI SPARQL endpoint;
- can be retrieved by using the COCI REST API;
- can be searched by using the COCI Search Interface;
- are also available as dumps on Figshare in CSV, N-Triples, and Scholix; and
- can be freely re-used for any purpose.