Columbia subject headings:
Europe--History--1871-1918.
Europe--History--1918-1945.
Harvard subject headings:
Europe--History--1871-1918.
Europe--History--1918-1945.
Europe--History--20th century.
Europe--Politics and government--20th century.
Princeton subject headings:
Europe--Economic conditions--20th century.
Europe--History--20th century.
Europe--Social conditions.