Columbia subject headings:
Internal security--Russia--History--20th century.
Spies--Russia--History--20th century.
World War, 1914-1918--Russia.
Harvard subject headings:
Counterrevolutions--Soviet Union.
Espionage, Soviet--Europe.
Russians--Europe--History--20th century.
Russians--Political activity--Europe--History--20th century.
Soviet Union--History--Revolution, 1917-1921--Secret service.
Princeton subject headings:
Internal security--Russia--History--20th century.
Spies--Russia--History--20th century.
World War, 1914-1918--Russia.