Columbia subject headings:
Economic development projects--Soviet Union--History--Sources.
GULag NKVD--History--Sources.
Hydraulic engineering--Soviet Union--History--Sources.
Internment camps--Soviet Union--History--Sources.
Nazi concentration camps--Soviet Union--History--Sources.
Railroads--Soviet Union--History--Sources.
Soviet Union--History--1925-1953--Sources.
Harvard subject headings:
Concentration camps--Soviet Union--History--Sources.
Economic development projects--Soviet Union--History--Sources.
GULag NKVD--History--Sources.
Hydraulic engineering--Soviet Union--History--Sources.
Railroads--Soviet Union--History--Sources.
Soviet Union--History--1925-1953--Sources.
Princeton subject headings:
Economic development projects--Soviet Union--History--Sources.
GULag NKVD--History--Sources.
Hydraulic engineering--Soviet Union--History--Sources.
Internment camps--Soviet Union--History--Sources.
Railroads--Soviet Union--History--Sources.
Soviet Union--History--1925-1953--Sources.