Columbia subject headings:
Operas--Librettos.
Operas--Scores.
Orpheus (Greek mythological character)--Drama.
Harvard subject headings:
Drama
Librettos
Operas
Operas--Librettos
Operas--Scores
Orpheus (Greek mythological character)--Drama.
Scores
Princeton subject headings:
Operas--Scores.
Operas.
Scores.