Columbia subject headings:
Harvard subject headings:
Europe--Civilization--19th century--Congresses.
Europe--Civilization--20th century--Congresses.
Politics and culture--Europe--History--19th century--Congresses.
Politics and culture--Europe--History--20th century--Congresses.
Princeton subject headings:
Europe--History--Congresses.
Europe--Politics and government--Congresses.
Europe--Relations--Congresses.