Columbia subject headings:
Harvard subject headings:
Berlin (Germany)--History--20th century.
Berlin (Germany)--Relations--Poland--Wrocław.
Wrocław (Poland)--History--20th century.
Wrocław (Poland)--Relations--Germany--Berlin.
Princeton subject headings:
Berlin (Germany)--History--20th century.
Berlin (Germany)--Relations--Poland--Wrocław.
Wrocław (Poland)--History--20th century.
Wrocław (Poland)--Relations--Germany--Berlin.