Columbia subject headings:
Opera--Stage-setting and scenery--History--Congresses.
Wagner, Richard, 1813-1883--Congresses.
Harvard subject headings:
Opera--Stage-setting and scenery
Wagner, Richard, 1813-1883
Princeton subject headings:
Opera--Stage-setting and scenery--History--Congresses.
Wagner, Richard, 1813-1883--Congresses.