Columbia subject headings:
Lortzing, Albert, 1801-1851--Congresses.
Opera--History--19th century--Congresses.
Harvard subject headings:
Lortzing, Albert, 1801-1851--Congresses.
Opera--History--19th century--Congresses.
Princeton subject headings:
Lortzing, Albert, 1801-1851--Congresses.
Opera--History--19th century--Congresses.