Columbia subject headings:
Socialism--Germany--History.
Sozialdemokratische Partei Deutschlands--History.
Working class--Germany--History.
Harvard subject headings:
Socialism--Germany--History
Sozialdemokratische Partei Deutschlands--History.
Working class--Germany--History.
Princeton subject headings:
Labor movement--Germany--History.
Socialism--Germany--History.
Sozialdemokratische Partei Deutschlands--History.