Columbia subject headings:
Harvard subject headings:
Concentration camps--History--20th century.
National socialism.
Princeton subject headings:
Internment camps--History--20th century--Congresses.
Nazi concentration camps--History--Congresses.
Political violence--History--20th century--Congresses.
Prisoners--History--20th century--Congresses.
Prisons--History--20th century--Congresses.