Columbia subject headings:
Harvard subject headings:
Concentration camps--Soviet Union--History--Sources.
Energy industries--Soviet Union--History--Sources.
Human rights--Soviet Union--History--Sources.
Political crimes and offenses--Soviet Union--History--Sources.
Princeton subject headings:
GULag NKVD--History--Sources.
Glavnoe upravlenie ispravitelʹno-trudovykh lagereĭ OGPU--History--Sources.
Political persecution--Soviet Union--History--Sources.
Power resources--Soviet Union--History--Sources.
Prisons--Soviet Union--History--Sources.
Soviet Union--History--1925-1953--Sources.
Stalin, Joseph, 1878-1953--Sources.