Columbia subject headings:
Harvard subject headings:
Ciechanów (Poland)--History--20th century--Congresses.
National socialism--Prussia, East (Poland and Russia)--Congresses.
Prussia, East (Poland and Russia)--History--20th century--Congresses.
World War, 1939-1945--Prussia, East (Poland and Russia)--Congresses.
Princeton subject headings:
Ciechanów (Poland)--History--20th century--Congresses.
National socialism--Prussia, East (Poland and Russia)--Congresses.
Prussia, East (Poland and Russia)--History--20th century--Congresses.
World War, 1939-1945--Prussia, East (Poland and Russia)--Congresses.