Columbia subject headings:
Socialism--Germany--Frankfurt am Main--History--19th century.
Working class--Germany--Frankfurt am Main--History--19th century.
Harvard subject headings:
Labor movement--Germany--Frankfurt am Main--History--19th century.
Socialism--Germany--Frankfurt am Main--19th century.
Socialism--Germany--Frankfurt am Main--History--19th century.
Working class--Germany--Frankfurt am Main--History--19th century.
Princeton subject headings:
Labor movement--Germany (West)--Frankfurt am Main--History--19th century.
Socialism--Germany (West)--Frankfurt am Main--History--19th century.