Columbia subject headings:
Harvard subject headings:
Europe--History--20th century--Congresses.
Russia--History--February Revolution, 1917--Congresses.
World War, 1914-1918--Congresses
World War, 1939-1945--Congresses.
Princeton subject headings:
Europe--History--20th century--Congresses.
Russia--History--February Revolution, 1917--Congresses.
World War, 1914-1918--Congresses.
World War, 1939-1945--Congresses.