Columbia subject headings:
Harvard subject headings:
Plebiscite--Germany--Prussia--History--Congresses.
Prussia (Germany)--Politics and government--1918-1933--Congresses.
Princeton subject headings:
Plebiscite--Poland--Prussia, West--History--Congresses.
Plebiscite--Prussia, East (Poland and Russia)--History--Congresses.
Prussia, East (Poland and Russia)--History--20th century--Congresses.
Prussia, West (Poland)--History--20th century--Congresses.