Wilson, Ivan F. and Victor S. Rocha. Geologic investigations in American republics, 1948: coal deposits of the Santa Clara district, near Tonichi, Sonora, Mexico.

Wilson, Ivan F. and Victor S. Rocha. Geologic investigations in American republics, 1948: coal deposits of the Santa Clara district, near Tonichi, Sonora, Mexico., Box: 14, Folder: 8. Campbell W. Pennington Papers, 33036864. Benson Latin American Collection, The University of Texas at Austin. https://archives.lib.utexas.edu/repositories/4/archival_objects/279399 Accessed September 26, 2026.