Columbia subject headings:
Harvard subject headings:
Espionage--Great Britain--History.
Espionage--Soviet Union--History.
Military intelligence--Great Britain--History--20th century
Military intelligence--Soviet Union--History.
Soviet Union--History--Revolution, 1917-1921--Secret service.
Spies--Great Britain.
Spies--Soviet Union.
Princeton subject headings:
Counterrevolutionaries--Soviet Union--History.
Espionage--Great Britain--History.
Espionage--Soviet Union--History.
Military intelligence--Great Britain--History--20th century.
Military intelligence--Soviet Union--History--20th century.
Soviet Union--History--Revolution, 1917-1921.
Spies--Great Britain.
Spies--Soviet Union.