Columbia subject headings:
Harvard subject headings:
Germany (East)--History--Sources.
Glavnoe upravlenie gosbezopasnosti NKVD--History--Sources.
Intelligence service--Soviet Union--History--Sources.
Internal security--Germany (East)--History--Sources.
Internal security--Germany (East)--Sources.
Soviet Union. Narodnyĭ komissariat gosudarstvennoĭ bezopasnosti--History--Sources.
Princeton subject headings:
Germany (East)--History--Sources.
Glavnoe upravlenie gosbezopasnosti NKVD--History--Sources.
Intelligence service--Soviet Union--History--Sources.
Internal security--Germany (East)--History--Sources.
Soviet Union. Narodnyĭ komissariat gosudarstvennoĭ bezopasnosti--History--Sources.