Within the shared cataloguing system subject headings are entered in structured form in fields 600–609 according to the principles of the chosen subject heading system (e.g. lists of subject headings or thesaurus). For uniform subject indexing in shared cataloguing, the COBISS General List of Subject Headings (SGC), which is also available as an authority database, is used, although subject headings from other systems can be added to records as well. The rules for subject indexing with the COBISS General List of Subject Headings (SGC) are described in the Subject indexing with SGC instruction manual, which is available on the SGC website https://www.cobiss.si/sgc/. When adding subject headings from other systems, the general directions, i.e. the basis for the term selection and subject phrase design to follow are the principles, which were presented in the publication Splošni slovenski geslovnik: navodila za predmetno označevanje knjižničnega gradiva in geslovnik. Ljubljana: Narodna in univerzitetna knjižnica, 2002, or principles from other recognized systems for subject analysis. E.g. for more detailed definition on the field of medicine the terms from MeSH (Medical Subject Headings) are used.

The establishment of the SGC authority database and the implementation of subject heading authority control in the shared cataloguing system have changed the way the data is entered in 60X fields has changed. SGC subject headings are not entered manually but are transferred from the authority database. The link between the authority records and subject headings in 60X fields is established via the subfield 60X3 – Authority record number.

When the subject headings are linked to SGC, do not enter the non-preferred forms in bibliographic records, whereas for other subject headings, they are entered in fields 960–969.

The retrieval goes simultaneously by fields 600–609 and 960–969. Fields 960–969 are linked to fields 600–609 with subfield 6 in which at both connected fields a two-digit number is entered (01–99).

Subfield 2 is used while entering fields 600–609 and 960–969; in subfield 2 the system code for subject headings is entered that is selected from the code list. If you use a local subject system in a local language that is not included in the code list, do not enter this subfield, but in every other case, this subfield is mandatory.

The following code list containing the system codes of subject headings is not completed and it is modified and updated according to actual needs:

Subfield 2 is also used at field 686 where codes from the code list for classification systems are entered. More detailed instructions are presented at field 686.