Columbia subject headings:
Museum der Arbeit (Hamburg, Germany)--Congresses.
Working class--Europe--History--19th century--Congresses.
Working class--Museums--Congresses.
Working class--Museums--Germany--Hamburg--Congresses.
Harvard subject headings:
Museum der Arbeit (Hamburg, Germany)--Congresses.
Working class--Europe--History--19th century--Congresses.
Working class--Museums--Congresses.
Working class--Museums--Germany--Hamburg--Congresses.
Princeton subject headings:
Working class--Europe--History--19th century--Congresses.
Working class--Europe--History--20th century--Congresses.