Columbia subject headings:
Harvard subject headings:
Germany--Politics and government--20th century
Plenge, Johann, 1874-1963
Socialism--Germany--20th century.
Socialists--Germany--Biography
Sociologists--Germany--Biography
Princeton subject headings:
Biographies.
Economists--Germany--Biography.
Plenge, Johann, 1874-1963.
Sociologists--Germany--Biography.