Looking back over 2024, we wanted to reflect on where we are in meeting our goals, and report on the progress and plans that affect you - our community of 21,000 organisational members as well as the vast number of research initiatives and scientific bodies that rely on Crossref metadata.
In this post, we will give an update on our roadmap, including what is completed, underway, and up next, and a bit about what’s paused and why.
The Crossref2024 annual meeting gathered our community for a packed agenda of updates, demos, and lively discussions on advancing our shared goals. The day was filled with insights and energy, from practical demos of Crossref’s latest API features to community reflections on the Research Nexus initiative and the Board elections.
Our Board elections are always the focal point of the Annual Meeting. We want to start reflecting on the day by congratulating our newly elected board members: Katharina Rieck from Austrian Science Fund (FWF), Lisa Schiff from California Digital Library, Aaron Wood from American Psychological Association, and Amanda Ward from Taylor and Francis, who will officially join (and re-join) in January 2025.
Background The Principles of Open Scholarly Infrastructure (POSI) provides a set of guidelines for operating open infrastructure in service to the scholarly community. It sets out 16 points to ensure that the infrastructure on which the scholarly and research communities rely is openly governed, sustainable, and replicable. Each POSI adopter regularly reviews progress, conducts periodic audits, and self-reports how they’re working towards each of the principles.
In 2020, Crossref’s board voted to adopt the Principles of Open Scholarly Infrastructure, and we completed our first self-audit.
In June 2022, we wrote a blog post “Rethinking staff travel, meetings, and events” outlining our new approach to staff travel, meetings, and events with the goal of not going back to ‘normal’ after the pandemic. We took into account three key areas:
The environment and climate change Inclusion Work/life balance We are aware that many of our members are also interested in minimizing their impacts on the environment, and we are overdue for an update on meeting our own commitments, so here goes our summary for the year 2023!
Sent to an HTTP(S) URL endpoint hosted by the member
Note that we don’t provide a plugin to directly display Cited-by results on a publisher website, although a community-developed plugin is available for OJS. The data from our APIs is delivered in XML or JSON format and needs to be parsed for display on a webpage.
Using a URL, you can retrieve all citations for a single DOI or prefix within a date range. You will need to provide your Crossref account credentials in the query.
If you use personal, individual user credentials, queries have the following format:
username is the shared role and password is the shared password for the prefix or title being retrieved;
doi can be a full DOI or a prefix.
On both versions of the query, date range is optional. Dates in the query refer to when the citation match was made (usually shortly after the DOI of the citing article was registered), not the publication date of the articles being queried for: all citations found in the given period will be returned, regardless of when the cited articles were originally deposited. Queries can also be made for a single day, in which case use the following format:
By default, citations from posted content (including preprints) are not included. To retrieve them as well, include &include_postedcontent=true in the query URL:
Output is XML formatted according to Crossref’s query schema.
If the query times out, we recommend using a smaller query, for example by using a narrower date range or splitting prefixes into individual DOIs. This is unlikely to affect most users, however if you frequently experience timeouts due to large query results get in touch.
Here is some example output:
<crossref_resultxmlns="http://0-www-crossref-org.libus.csd.mu.edu/qrschema/2.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"version="2.0"xsi:schemaLocation="http://0-www-crossref-org.libus.csd.mu.edu/qrschema/2.0 http://0-www-crossref-org.libus.csd.mu.edu/qrschema/crossref_query_output2.0.xsd"><query_result><head><email_address>none</email_address><doi_batch_id>none</doi_batch_id></head><body></forward_link><forward_linkdoi="10.1021/jacs.9b09811"><journal_citefl_count="0"><issntype="print">2161-1653</issn><issntype="electronic">2161-1653</issn><journal_title>ACS Macro Letters</journal_title><journal_abbreviation>ACS Macro Lett.</journal_abbreviation><article_title>Critical Role of Ion Exchange Conditions on the Properties of Network Ionic Polymers</article_title><contributors><contributorfirst-author="true"sequence="first"contributor_role="author"><given_name>Naisong</given_name><surname>Shan</surname></contributor><contributorfirst-author="false"sequence="additional"contributor_role="author"><given_name>Chengtian</given_name><surname>Shen</surname></contributor><contributorfirst-author="false"sequence="additional"contributor_role="author"><given_name>Christopher M.</given_name><surname>Evans</surname></contributor></contributors><volume>9</volume><issue>12</issue><first_page>1718</first_page><year>2020</year><publication_type>full_text</publication_type><doitype="journal_article">10.1021/acsmacrolett.0c00678</doi></journal_cite></forward_link></body></query_result></crossref_result>
Note that the fl_count property gives the number of times the citing article has itself been cited.
Retrieve citation matches using an XML query
Citations can be retrieved through an XML query. The query contains only the DOI of the cited article stored in the fl_query element. Each XML file must contain only a single DOI.
If you submit a batch query submission with more than one DOI per query, the remaining DOIs in that query will return the message “exceeded limit of forward link queries per submission.” So, any DOIs after the first will not have alerts enabled.
Setting the alert attribute to “true” instructs the system to remember this query and to send new Cited-by link results to the specified email address when they occur. Note that an email address cannot be unset from receiving notifications, so only use this option for email addresses that will continue to receive notifications on a long-term basis.
By default, citations from posted content (including preprints) are not included. To retrieve them as well, use <fl_query include_postedcontent="true"> in the body of the query.
Here is an example of the output XML:
<crossref_resultxmlns="http://0-www-crossref-org.libus.csd.mu.edu/qrschema/2.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"version="2.0"xsi:schemaLocation="http://0-www-crossref-org.libus.csd.mu.edu/qrschema/2.0 http://0-www-crossref-org.libus.csd.mu.edu/qrschema/crossref_query_output2.0.xsd"><query_result><head><email_address>{email}</email_address><doi_batch_id>fl_001</doi_batch_id></head><body><forward_linkdoi="10.5555/ums71316"><journal_citefl_count="0"><issntype="print">1070-3632</issn><issntype="electronic">1608-3350</issn><journal_title>Russian Journal of General Chemistry</journal_title><journal_abbreviation>Russ J Gen Chem</journal_abbreviation><article_title>Simultaneous Formation of Cage and Spirane Pentaalkoxyphosphoranes in Reaction of 5,5-Dimethyl-2-(2-oxo-1,2-diphenylethoxy)-1,3,2-dioxaphosphorinane with Hexafluoroacetone</article_title><contributors><contributorfirst-author="true"sequence="first"contributor_role="author"><given_name>V. F.</given_name><surname>Mironov</surname></contributor><contributorfirst-author="false"sequence="additional"contributor_role="author"><given_name>M. N.</given_name><surname>Dimukhametov</surname></contributor><contributorfirst-author="false"sequence="additional"contributor_role="author"><given_name>Ya. S.</given_name><surname>Blinova</surname></contributor><contributorfirst-author="false"sequence="additional"contributor_role="author"><given_name>F. Kh.</given_name><surname>Karataeva</surname></contributor></contributors><volume>90</volume><issue>11</issue><first_page>2080</first_page><year>2020</year><publication_type>full_text</publication_type><doitype="journal_article">10.1134/S1070363220110109</doi></journal_cite></forward_link></body></query_result></crossref_result>
Retrieve citation matches using the admin tool
You can find citations to single DOIs using our admin tool. Log in using your Crossref account credentials, click on the Queries tab, then Cited By Links. This returns a list of DOIs:
Retrieve citation matches using the OJS Cited-by plugin
For members who manage their journal using OJS v3.1.2.4 or later, you can install a Cited-by plugin from the plugin gallery. It pulls data from the Cited-by API and can display it directly on article webpages. This plugin has been generously contributed by the community and is not maintained by Crossref.
If you are not using OJS but use another third party software to manage your journal there is a good chance that there is also a plugin available. We don’t maintain a comprehensive list of Cited-by plugins, but you can contact your software provider for details.
Retrieve citation matches using OAI-PMH
Note that the OAI-PMH API returns matches for the following article types: Journals, Books, Book Series, and Components. Other types are not included. To get complete results, we recommend using the HTTPS POST or an XML query (see the two sections above) for retrieving Cited-by matches rather than OAI-PMH.
This format retrieves Cited-by matches established within a date range for a prefix or title. Queries have the following format:
role and password are the role credentials for the prefix or title being retrieved;
record type is a single letter. Use J for journal; B for books, conference proceedings, datasets, reports, standards, or dissertations; and S for series;
prefix is the owning prefix of the title being retrieved;
pubID is the publication identification number of the title. This is optional: to query for all titles related to a prefix, simply omit the pubID;
metadataPrefix=cr_citedby indicates that the results should include Cited-by matches rather than item metadata.
The from and until parameters are optional and define a date range using YYYY-MM-DD format (ISO 8601). Items returned were cited at least once in the period. All citations for these items are returned, not only those that occurred between the two dates. Note that the date range does not refer to the publication date of the cited works, but the dates they were cited.
By default, citations from posted content (including preprints) are not included. To retrieve them as well, add &include_postedcontent=true to the query URL.
Output is XML formatted according to our query schema and contains a list of the DOIs that cited the specified article or prefix.
Some OAI-PMH requests are too big to be retrieved in a single transaction. If a given response contains a resumption token, the user must make an additional request to retrieve the rest of the data. Learn more about resumption tokens, and OAI-PMH requests.
OAI-PMH queries return the DOI of each citation. You can use our REST API or XML API to retrieve the full bibliographic data for each citation.
Citation notifications
You can receive citation notifications by email or an endpoint notification. In both cases the text of the message is the same: it contains the same output as an XML query, containing details of the citing and cited works.
To select an email address for Cited-by notifications, see the XML query section.
Troubleshooting Cited-by queries
Sometimes citations don’t show up in Cited-by when you would expect them. There could be several reasons for this:
The references haven’t been included in the metadata. We don’t use article PDFs or crawl websites to retrieve references, we rely on them being deposited as metadata by our members. Check the metadata of the citing work using our APIs to see whether references have been included.
The DOI of the cited work wasn’t included in the reference and there was either an error in the metadata or insufficient information for us to make a reliable match. In this case, check the metadata for any errors and contact the owner of the citing work to redeposit the references.
If the citing article was registered very recently it can take time to update the cited article’s metadata. If this happens, wait for a few days before trying again.
Note that citations are only retrieved from works with a Crossref DOI and will differ from citation counts provided by other services. Not all scholarly publications are registered with us and not all publishers opt to deposit references, so we can’t claim that citation counts are comprehensive.
If you have difficulty accessing citation matches for your own content, try checking first with the admin tool and see if you can replicate the results there using one of the API options above.
Page owner: Isaac Farley | Last updated 2023-April-28
