Columbia subject headings:
Opera--19th century.
Verdi, Giuseppe, 1813-1901--Criticism and interpretation.
Wagner, Richard, 1813-1883--Criticism and interpretation.
Harvard subject headings:
Harmony.
Opera--19th century
Verdi, Giuseppe, 1813-1901--Criticism and interpretation.
Wagner, Richard, 1813-1883--Criticism and interpretation.
Princeton subject headings:
Opera--19th century.
Verdi, Giuseppe, 1813-1901--Criticism and interpretation.
Wagner, Richard, 1813-1883--Criticism and interpretation.