Columbia subject headings:
Harvard subject headings:
Europe, Central--History--19th century--Congresses.
Europe, Central--History--20th century--Congresses.
Europe, Eastern--History--19th century--Congresses.
Europe, Eastern--History--20th century--Congresses.
Princeton subject headings:
Europe, Central--History--19th century--Congresses.
Europe, Central--History--20th century--Congresses.
Europe, Eastern--History--19th century--Congresses.
Europe, Eastern--History--20th century--Congresses.