Columbia subject headings:
Hirschfeld, Robert, 1857-1914.
Hof-Operntheater (Vienna, Austria)
Mahler, Gustav, 1860-1911--Criticism and interpretation.
Harvard subject headings:
Hof-Operntheater (Vienna, Austria)
Mahler, Gustav, 1860-1911.
Weingartner, Felix, 1863-1942.
Princeton subject headings: