Columbia subject headings:
Mexico--Politics and government--1910-1946.
Mexico--Politics and government--1946-1970.
Working class--Political activity--Mexico--History--20th century.
Harvard subject headings:
Labor unions--Mexico--History--20th century.
Mexico--Politics and government--1910-1946.
Mexico--Politics and government--1946-1970
Princeton subject headings:
Labor movement--Mexico--History.
Labor unions--Mexico--History.