Walker, Harlan A. Mining methods and costs at El Potosí Mine, El Potosi Mining Co., Chihuahua, Mexico, Information Circular 6804Washington, D.C.: United States Bureau of Mines, 1934 November

Walker, Harlan A. Mining methods and costs at El Potosí Mine, El Potosi Mining Co., Chihuahua, Mexico, Information Circular 6804Washington, D.C.: United States Bureau of Mines, 1934 November, Box: 2, Folder: 6. El Potosí Mining Company Records, 33399703. Benson Latin American Collection, The University of Texas at Austin. https://archives.lib.utexas.edu/repositories/4/archival_objects/263492 Accessed September 25, 2026.