Formatted citations are sometimes referred to as "plain text references." For example, an APA formatted citation for the DOI 10.1038/nclimate1398 is:
Hungate, B. A., & Hampton, H. M. (2012). Ecosystem services: Valuing ecosystems for climate. Nature Climate Change, 2(3), 151-152. https://doi.org/10.1038/nclimate1398
Crossref has two interfaces that can be used for making formatted citation queries:
- Simple Text Query (STQ): a tool which allows a user to cut-and-paste references into an interactive form and receive instant results or to upload a text file and receive HTML format results via email.
- XML API: supports XML-formatted queries via HTTPS POST and GET.
RefXpress is a powerful citation parser, meaning citations are broken up into their parts (publication title, author, volume, issue, page, publication date, etc.). These parts can then easily be transformed into an XML query.
Crossref also has some reference-parsing capability. We are able to establish matches for many well-formatted citations. This means that if you exceed your RefXpress usage allotment we'll continue to process your queries, but the number of matches will probably drop considerably.
The tools backed by RefXpress meets the needs of nearly all individuals and many very small publishers. Crossref licenses RefXpress from Inera and pays a per transaction fee and therefore is not able to provide unlimited free access to Crossref STQ or API users. RefXpress is the default back-end used by Crossref’s Simple Text Query tools. Queries are limited to 1,000 successful matches per month for each user.
Please do not create/register multiple email accounts to circumvent this measure. Crossref monitors activity and may block querying for abusers or direct STQ activity to the FCS servicing technology.
In some cases additional usage may be made available or arrangements may be made to provide metered service for a fee. RefXpress may also be enabled for use via the HTTP API for Crossref members but usage limits will have to be enforced.