Columbia subject headings:
Industries--Mexico--Hidalgo del Parral--History.
Silver mines and mining--Mexico--Hidalgo del Parral--History.
Harvard subject headings:
Industries--Mexico--Hidalgo del Parral--History.
Silver mines and mining--Mexico--Hidalgo del Parral--History.
Princeton subject headings:
Hidalgo del Parral (Mexico)--History.
Mineral industries--Mexico--History.
Villa Escobedo (Mexico)--History.