Columbia subject headings:
Harvard subject headings:
Industries--Denmark--History--19th century--Congresses.
Industries--Germany, Northern--History--19th century--Congresses.
Industries--Germany--Schleswig-Holstein--History--19th century--Congresses.
Princeton subject headings:
Denmark--Economic conditions.
Germany, Northern--Economic conditions.
Industries--Denmark--History.
Industries--Germany, Northern--History.
Industries--Germany--Schleswig-Holstein.
Schleswig-Holstein (Germany)--Economic conditions.