Columbia subject headings:
Harvard subject headings:
Calles, Plutarco Elías, 1877-1945.
Confederación Regional Obrera Mexicana--History.
Working class--Mexico--Political activity--History.
Working class--Political activity--Mexico--History.
Princeton subject headings:
Calles, Plutarco Elías, 1877-1945.
Mexico--Politics and government--1910-1946.