Columbia subject headings:
Harvard subject headings:
Europe--Foreign relations--1989---Congresses.
International organization--History--Congresses.
International relations--History--Congresses.
World politics--1989---Congresses
Princeton subject headings:
Geopolitics--20th century--Congresses.
Geopolitics--21st century--Congresses.
International organization--Congresses.
International relations--Congresses.
Security, International--Congresses.
World politics--20th century--Congresses.
World politics--21st century--Congresses.