Columbia subject headings:
Operas--Bibliography--Catalogs.
University of California, Berkeley. Music Library--Catalogs.
University of California, Los Angeles. Music Library--Catalogs.
Harvard subject headings:
Operas--Bibliography--Catalogs.
University of California, Berkeley. Music Library--Catalogs.
University of California, Los Angeles. Music Library--Catalogs.
Princeton subject headings:
Operas--Bibliography--Catalogs.