Columbia subject headings:
Germany--Foreign relations--Soviet Union.
Soviet Union--Foreign relations--Germany.
World War, 1914-1918--Causes.
Harvard subject headings:
Germany--Foreign relations--Soviet Union.
Soviet Union--Foreign relations--Germany.
World War, 1914-1918--Causes
Princeton subject headings:
Germany--Foreign relations--Russia.
Russia--Foreign relations--Germany.
World War, 1914-1918--Causes.