Columbia subject headings:
Chad--Economic conditions--1960-
Chad--History--21st century.
Chad--Politics and government--1990-
Harvard subject headings:
Chad--Economic conditions--1960-
Chad--Economic conditions--21st century.
Chad--History--21st century.
Chad--Politics and government--1990-
Princeton subject headings:
Chad--Economic conditions--21st century.
Chad--History--21st century.
Chad--Politics and government--1990-