Columbia subject headings:
Harvard subject headings:
El Oro (Mexico)--Economic conditions.
Labor movement--Mexico--El Oro--History.
Miners--Mexico--El Oro--History.
Strikes and lockouts--Miners--Mexico--El Oro--History.
Princeton subject headings:
El Oro (Mexico)--Economic conditions.
Labor movement--Mexico--El Oro--History.
Miners--Mexico--El Oro--History.
Strikes and lockouts--Miners--Mexico--El Oro--History.