The registration agency Crossref, in addition to the registration service of digital identifiers DOI, provides a number of other services, namely:
CrossRef Reference Linking is a database of mutual quoting of scientific information materials. Used to calculate the citation indexes of scientific publications;
CrossRef Plagiarism Check - a system for tracking the originality of scientific publications and the search for plagiarism (works at the stage of preparing materials for printing);
CrossRef Crossmark is a version control system for scientific publications that allows you to track reissues, additions, corrections, error messages, etc.
CrossRef Funding Registry - a database of information on the sources of funding publications. Used to record and analyze the effectiveness of the use of funds from scientific grants.
Crossref Cited-by allows you to automatically determine and calculate reciprocal citations in scientific publications