Columbia subject headings:
Europe--History--1871-1918--Congresses.
Europe--History--1918-1945--Congresses.
Revolutions--Europe--History--Congresses.
Harvard subject headings:
Europe--History--1871-1918--Congresses.
Europe--History--1918-1945--Congresses.
Revolutions--Europe--History--Congresses.
Princeton subject headings:
Europe--History--1871-1918--Congresses.
Europe--History--1918-1945--Congresses.
Revolutions--Europe--History--Congresses.