Columbia subject headings:
Harvard subject headings:
Oldenburg (Germany : State)--History--20th century.
Oldenburg (Germany : State)--Politics and government--20th century.
World War, 1914-1918--Germany--Oldenburg (State)
Princeton subject headings:
Germany--History--Revolution, 1918.
Oldenburg (Germany : State)--History--20th century--Sources.
Oldenburg (Germany : State)--Politics and government--20th century--Sources.