If in a body’s publication its full form of name and its initials both appear formally in the same source, choose the full form for use in the heading. (Change the heading if later evidence shows a clear pattern of predominant usage that differs from the heading chosen.)

When a corporate name must be established for an item not issued by the corporate body, treat the item being cataloged as a reference source. If the item provides both the body’s full form of name and its initials, choose the full form for use in the heading (even if the initials appear prominently and the full form does not).

If variant forms appear formally in chief sources of the body’s publications, choose the predominant form. If an initial form (including an acronym) appears prominently, check the authority file to see if there is a reference or a heading for another body already under the same initials. If there is, this means the initials do not "differentiate" and thus the full form must be adopted as the AACR2 form.

See also:

24.2. Variant Names. General Rules