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Updates from Europe PMC, a global database of life sciences literature

Europe PMC team

 | 16 February 2018


Why every researcher should care about open citations

What happens when you cite someone’s research?

As you write a research publication you include references to the work of your fellow researchers. Once the article is published in a scientific journal the readers may view the reference list to verify cited information or perhaps discover additional studies relevant to their topic. But have you ever wondered what happens with citation data that you produce and how it is being used by others?

Once the article is accepted for publication, many journal publishers will submit the article record to Crossref in order to obtain a DOI for the paper. This record will include article metadata: author names, affiliations, article title, journal name, etc. Often the publisher will also submit the references of articles in their journals to access the Cited-By Service provided by Crossref. This citation data is not released automatically – by default the references are hidden from the public eye and can only be obtained from Crossref with specific consent from the publisher.

Why do we need citations to be open?

Open citation data can be put to a good use. It improves the discoverability of the scholarly content and helps to trace knowledge back to its sources. It allows the discovery of connections within scientific research, demonstrating how a single finding may be used by scholars in different disciplines and countries. It can reveal shared authorship or common funding. Citation data is used to calculate citation rates, and can help create new transparent indicators for research evaluation.

Setting citations free: the Initiative for Open Citations

Despite its potential, the bulk of citation data has been difficult to find and access until recently. With the launch of the Initiative for Open Citations (I4OC) on April 6th, 2017 much of the previously unavailable citation data has been liberated. The I4OC has encouraged many scholarly publishers to make the references they deposit with Crossref open. Thanks to their efforts, the share of freely available citation data in Crossref has grown from 1% to over 50% (as of February 2018).


What free tools are built on open citation data?

Europe PMC hosts an extensive collection of biomedical research papers, which is supplemented by an open citation network – freely available without subscription. The citation data is mainly determined from the Europe PMC content and is further supplemented with metadata supplied by Crossref. Since the launch of the I4OC the number of citations added monthly to Europe PMC via Crossref has nearly doubled. While 7.1 million references were ingested from May to October in 2016, this number has grown to 14.9 million references for the same period in 2017. As of February 2018 the Europe PMC citation network contains 316,930,434 citation links for 12.8 million citing records – nearly 44% of the 29 million journal articles.
Citation data in Europe PMC can be accessed programmatically using the citations or references modules of the RESTful or SOAP APIs. Each module returns bibliographic information: article identifier, title, author’s list, publication year, citation counts, etc. In combination with other services within Europe PMC developers’ suite, such as the Annotations API or Grants API, it represents a powerful tool for citation analysis.

Website users can access reference lists and cited-by information for a particular article in the Citation tab.

They can also use advanced search settings to retrieve publications that have been cited a certain number of times, or to access papers co-cited together.

An important thing to mention here, is that citation information is matched to Europe PMC records based on available metadata. This means that if a citation can be confidently identified, it will appear as a publication link. Readers can thus follow the reference trail through the citation network, and find research relevant to their area.

Open citation data also enables development of the powerful discovery tools. For example, in Europe PMC it is possible to sort search results by the number of citations to find the most highly cited articles on a particular topic. Citation counts for each paper are also displayed in the results list.

The cited-by information available via the Citations tab is also represented visually in a citation graph. Readers can view citation graphs on the abstract or full text page of the publication. The graph shows how frequently a paper has been referenced over time. Hovering over individual graph points brings up the number of citations for each year.

Another Europe PMC feature built using open citation data are author profiles. An author profile provides a graphical overview of the author’s academic output. It is generated automatically for every researcher with a public ORCID record and ‘claimed’ works available in Europe PMC. The profile contains a publication graph showing the number of papers for any given year and a yearly citation count. Open access articles are highlighted in blue, with a darker shade representing articles licensed for reuse.

Each individual record in the profile is also displayed in the publication list together with the already familiar citation graph based on open citations. Users can sort the list by date or times cited, to see which of the works had higher impact in terms of citations.

The number of author profiles in Europe PMC is growing constantly and currently combines information for more than 650,000 biomedical researchers and over 5 million articles. To help users easily retrieve author information we have implemented a Suggested Authors feature. For an author search that matches a researcher with ORCID, a user will see a suggested authors box at the top of their results list. It will display author information for the two most prolific researchers, including their affiliation (if available), the number of publications and the number of citations. Users can then go directly to the profile page of the author using the link provided.

Taking action

Citations stitch together the global web of scholarly knowledge. To make the most of the open citations, please support the I4OC in their bold ambition: to make all citation data freely available for reuse. Get the word out about the initiative, ask journals in which you publish or do peer review to open up their citations, and finally – use the open citations in your own research and demonstrate the value of the open scholarship.

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Europe PMC is a service of the Europe PMC Funders' Group, in partnership with EMBL’s European Bioinformatics Institute (EMBL-EBI); and in cooperation with the National Center for Biotechnology Information (NCBI) at the U.S. National Library of Medicine (NCBI/NLM) . It includes content provided to the PubMed Central (NLM/PMC) archive by participating publishers.