Columbia subject headings:
Harvard subject headings:
Espionage, German--Soviet Union.
Germany--Foreign relations--Soviet Union.
Intelligence service--Germany--History.
Secret service--Germany--History.
Soviet Union--Foreign relations--Germany.
Princeton subject headings:
Espionage, German--Europe, Eastern--History--20th century.
Europe, Eastern--Foreign relations--Germany.
Germany--Foreign relations--Europe, Eastern.
Military intelligence--Germany--History.
Secret service--Germany.