From a Post by on the OpenCitations Blog:
COCI is the OpenCitations Index of Crossref open DOI-to-DOI citations, all released as CC0 material…
COCI is our first OpenCitations Index of open citations, in which we have applied the concept of citations as first-class data entities, each identified using a unique persistent Open Citation Identifier (OCI), to index the contents of one of the major databases of open scholarly citation information, namely Crossref, and to render and make available this information in machine-readable RDF.
We are now proud to announce the third release of COCI, which contains more than 624 million DOI-to-DOI citation links coming from both ‘the ‘Open’ and the ‘Limited’ sets of Crossref reference data. This represents an increase of 40% in the number of indexed citations, compared with the second release of COCI on 12th November 2018, which indexed more than 445 million citations.
Access COCI Data