Subfield code: $6 - Linkage
Subfield $6 contains data that links fields that are different script representations of each other. Subfield $6 may contain the tag number of an associated field, an occurrence number, a code that identifies the first script encountered in a left-to-right scan of the field, and an indication that the orientation for a display of the field data is right-to-left. A regular (non-880) field may be linked to one or more 880 fields that all contain different script representations of the same data. Subfield $6 is always the first subfield in the field.
A complete description of subfield $6 is found in Appendix A: Control Subfields in each format. Guidelines for applying it are also provided in the 880 (Alternate Graphic Representation) description in each format.
See also:
Appendix A: Control Subfields (Authority)
Appendix A: Control Subfields (Bibliographic)
Appendix A: Control Subfields (Classification)
Appendix A: Control Subfields (Community Information)
Appendix A: Control Subfields (Holdings)