Columbia subject headings:
Harvard subject headings:
Mexico--Politics and government--20th century.
Partido de la Revolución Democrática (Mexico)--History.
Political parties--Mexico--History--20th century
Princeton subject headings:
Mexico--Politics and government--1970-1988.
Mexico--Politics and government--1988-2000.
Partido de la Revolución Democrática (Mexico)
Political parties--Mexico--History--20th century.