Columbia subject headings:
Harvard subject headings:
Frankfurt am Main (Germany)--History--20th century.
Frankfurt am Main (Germany)--Politics and government--20th century.
Socialism--Germany--Frankfurt am Main.
Princeton subject headings:
Anarchism--Germany--History--20th century.
Communism--Germany--History--20th century.
Frankfurt am Main (Germany)--History.
Germany--History--1933-1945.
Socialism--Germany--History--20th century.