From the Open Citations Index (COCI) Blog:
Every two months we are able to publish additions to COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations. This latest release (dated 4 July 2020) extended COCI with more than 18 million additional citations, so that COCI now contains more than 721 million DOI-to-DOI citation links between more than 58.8 million bibliographic entities.
Learn More About the Latest Release and More COCI News
Direct to OpenCitations Index Website