Columbia subject headings:
Metastasio, Pietro, 1698-1782--Criticism and interpretation.
Operas--Librettos.
Harvard subject headings:
Libretto--18th century.
Metastasio, Pietro, 1698-1782--Congresses.
Metastasio, Pietro, 1698-1782--Criticism and interpretation--Congresses.
Princeton subject headings:
Libretto--18th century.
Metastasio, Pietro, 1698-1782--Criticism and interpretation--Congresses.