Columbia subject headings:
Harvard subject headings:
Infrastructure (Economics)--Germany--Schleswig-Holstein--History--20th century--Congresses.
Schleswig-Holstein (Germany)--Economic conditions--20th century--Congresses.
Schleswig-Holstein (Germany)--Social conditions--20th century--Congresses.
Princeton subject headings:
Infrastructure (Economics)--Germany--Schleswig-Holstein--History--20th century--Congresses.
Schleswig-Holstein (Germany)--Economic conditions--20th century--Congresses.
Schleswig-Holstein (Germany)--Social conditions--20th century--Congresses.