Columbia subject headings:
Choral societies--Germany--History--20th century.
Socialism and theater--Germany--History--20th century.
Socialism--Germany--Societies, etc.--History--20th century.
Harvard subject headings:
Choral societies--Germany.
Working-men's clubs--Germany--History and criticism.
Princeton subject headings:
Workers' theater--Germany.
Working class--Germany.
Working class--Songs and music.