Indicator values are not defined.

Since subfields contained by the field 993 have been designated in general as subfield a, subfield b etc., libraries that are going to use this field for their local database should define the uniform purpose of these subfields. It is recommended to the libraries to prepare internal instructions for using this field, which must be considered by every cataloguer from a particular library. First of all the data must be defined, which should be entered in a particular subfield. At the same time, the library must provide the form, structure and quality of entered data. If data entry requires repeatable subfields, the repeating order of subfields must also be defined (e.g. successive repeating of the same subfield or repeating of a group of subfields containing two or more successive subfields). As for the planning implementation of the field 993, libraries should consult the national COBISS Centre.

Field 993 is not saved in COBIB. Since every library can use it in different way, this field is not suitable to use in such applications which require the uniform date structure, e.g. in COBISS/OPAC, in standard defined displays etc. The field is indexed and it is used only for searching a local database, and only for user defined display formats on local level within the shared cataloguing software.