Columbia subject headings:
Working class--Germany--History--20th century.
Harvard subject headings:
Germany--Social conditions--Congresses.
Social security--Germany--History--20th century.
Working class--Germany--History--20th century
Working class--Germany--History--20th century--Congresses.
Working class--Germany--Social conditions--Congresses.
Princeton subject headings:
Working class--Germany--History--20th century.