Columbia subject headings:
Labor unions and communism--Germany--Schleswig-Holstein--History--Congresses.
Labor unions--Germany--Schleswig-Holstein--History--Congresses.
Schleswig-Holstein (Germany)--Economic conditions--Congresses.
Working class--Germany--Schleswig-Holstein--History--Congresses.
Harvard subject headings:
Labor unions and communism--Germany--Schleswig-Holstein--History--Congresses.
Labor unions--Germany--Schleswig-Holstein--History--Congresses.
Schleswig-Holstein (Germany)--Economic conditions--Congresses.
Working class--Germany--Schleswig-Holstein--History--Congresses.
Princeton subject headings:
Labor movement--Germany (West)--Schleswig-Holstein--History.
Labor unions--Germany (West)--Schleswig-Holstein--History.
Socialism--Germany (West)--Schleswig-Holstein--History.