Columbia subject headings:
Deutscher Zollverein--History.
Germany--Economic integration--History.
Hesse (Germany)--Commerce--History.
Tariff--Germany--History.
Harvard subject headings:
Deutscher Zollverein--History.
Germany--Economic conditions.
Hesse (Germany)--Commerce--History.
Tariff--Germany--History.
Princeton subject headings:
Deutscher Zollverein.
Hesse (Germany)--Commerce--History.
Hesse (Germany)--Economic conditions.