Columbia subject headings:
Harvard subject headings:
Duisburg (Germany)--History.
Labor unions--Germany--Duisburg--History--19th century.
Sozialdemokratische Partei Deutschlands--History--19th century.
Working class--Germany--Duisburg--History--19th century.
Princeton subject headings:
Duisburg (Germany)--History.
Labor movement--Germany (West)--Duisburg--History--19th century.
Labor unions--Germany (West)--Duisburg--History--19th century.
Sozialdemokratische Partei Deutschlands--History--19th century.