Columbia subject headings:
Opera--19th century--Congresses.
Verdi, Giuseppe, 1813-1901--Anniversaries, etc.
Verdi, Giuseppe, 1813-1901--Congresses.
Wagner, Richard, 1813-1883--Anniversaries, etc.
Wagner, Richard, 1813-1883--Congresses.
Harvard subject headings:
Opera--19th century--Congresses.
Verdi, Giuseppe, 1813-1901--Anniversaries, etc.
Verdi, Giuseppe, 1813-1901--Congresses.
Wagner, Richard, 1813-1883--Anniversaries, etc.
Wagner, Richard, 1813-1883--Congresses.
Princeton subject headings:
Opera--19th century--Congresses.
Verdi, Giuseppe, 1813-1901--Anniversaries, etc.--Congresses.
Verdi, Giuseppe, 1813-1901--Congresses.
Wagner, Richard, 1813-1883--Anniversaries, etc.--Congresses.
Wagner, Richard, 1813-1883--Congresses.