MLA BP
Music Library Association Best Practices for Music Cataloging Using RDA and MARC21 for Chapter 24: General Guidelines on Recording Relationships between Works, Expressions, Manifestations, and Items
MLA BP for 24.4.1
IDENTIFIER FOR THE RELATED WORK, EXPRESSION, MANIFESTATION, OR ITEM
MLA recommendation: Follow , that is, generally provide access points when referencing related works and expressions, and structured or unstructured descriptions when referencing related manifestations and items. Identifiers are not used alone to express such relationships in the current MARC environment.
MLA BP for 24.5
RELATIONSHIP DESIGNATOR
MLA recommendation: Generally give relationship designators for all works and expressions for which access points are given.1
For further information, see PCC Guidelines for the Application of Relationship Designators in Bibliographic Records.