Columbia subject headings:
Nazi concentration camps--Germany--Emsland.
Political prisoners--Germany--Emsland.
Postal service--Germany--Emsland--History.
World War, 1939-1945--Postal service.
World War, 1939-1945--Prisoners and prisons, German.
Harvard subject headings:
Princeton subject headings:
Postage stamps--Germany--Catalogs.
Prisoners of war--Postal service.
World War, 1939-1945--Concentration camps--Germany--Emsland.
World War, 1939-1945--Prisoners and prisons, German.