Columbia subject headings:
Harvard subject headings:
Europe--History--20th century--Congresses.
Germany--History--20th century--Congresses.
Switzerland--History--20th century--Congresses.
Switzerland--Politics and government--20th century--Congresses.
Switzerland--Relations--20th century--Congresses.
Princeton subject headings:
Europe--History--20th century--Congresses.
Germany--History--20th century--Congresses.
Switzerland--History--20th century--Congresses.
Switzerland--Politics and government--20th century--Congresses.
Switzerland--Relations--20th century--Congresses.