Columbia subject headings:
Socialism--Europe--History--20th century.
Socialism--History--20th century.
World War, 1914-1918.
Harvard subject headings:
Socialism--Europe--20th century.
Socialism--Europe--History--20th century
Socialism--History--20th century
World War, 1914-1918.
Princeton subject headings:
Socialism--Europe--History--20th century.
Socialism--History--20th century.
World War, 1914-1918.