This page is a legacy page (not linked anymore from the official website) that describes POCI. Since October 2023, all the citation data collected previously in different OpenCitations Indexes have been moved (and deduplicated) in the new citation collection, i.e. the OpenCitations Index.
POCI, the OpenCitations Index of PubMed open PMID-to-PMID citations, is an RDF dataset containing details of all the citations from publications bearing PubMed Identifiers (PMIDs) to other PMID-identified publications, harvested from the National Institutes of Health Open Citations Collection (NIH-OCC). The citations available in POCI are treated as first-class data entities, with accompanying properties including the citations timespan, modelled according to the OpenCitations Data Model.
Currently, POCI contains:
717,654,703 citations;
29,005,551 bibliographic resources.
POCI was first created and released on 27 December 2022.
Most recent update of POCI: December 2022, based on the dump of NIH Open Citation Collection dated November 2022.
Each citation (i.e. an individual of the class cito:Citation) is identified by an URL structured as follows: https://w3id.org/oc/index/poci/ci/[[OCI]].
Each Open Citation Identifier [[OCI]] has a simple structure: the lower-case letters "oci" followed by a colon, followed by two numbers separated by a dash (e.g. https://w3id.org/oc/index/poci/ci/01600102060800080706-016002060909030401), in which the first number identifies the citing work and the second number identifies the cited work.
For citations in which the citing and cited works are identified by PMIDs, which includes all the POCI citations, the OCI is created in the following manner, as explained more fully here. Each converted numeral part of OCI is prefixes by a 0160
, which indicates that NIH is the supplier of the original metadata of the citation (as indicated at http://opencitations.net/oci).
OCIs can be resolved using the OpenCitations OCI Resolution Service.
All the data in POCI:
by querying the SPARQL endpoint of POCI, DOCI and CROCI;
can be retrieved using the POCI REST API;
are available as dumps on Figshare in CSV, N-Triples and Scholix.