Columbia subject headings:
Yemen (Republic)--History--1962-1972.
Yemen (Republic)--History--1972-1990.
Yemen (Republic)--History--Unification, 1990.
Harvard subject headings:
Yemen (Republic)--History--1962-1972.
Yemen (Republic)--History--1972-1990.
Yemen (Republic)--History--Unification, 1990.
Princeton subject headings: