DOI is the unique index consisting of letters and numbers. It is assigned individually to the certain author's scientific work officially published and presented as the electronic-digital object (report, article, monograph, book chapter etc.). The DOI facilitates the search and identification of the scientific work through access to the electronic publication on the corresponding Internet-resource (website). The CrossRef (www.crossref.org) service is responsible for generation of DOI-indexes, introduction of information about publications into the international database, as well as ensuring access to scientific publications.

The cost of indexation in the CrossRef system (including the assignment of the individual DOI-index) for every publication presented in the Socrates–Notion is 5.00 €.