Also available online in PDF format from the U.S. Geological Survey Warehouse (http://pubs.er.usgs.gov/).
"Prepared in cooperation with the Dirección General de Minas y Petróleo, Secretaría de la Economía Nacional de México, and the Instituto de Geología, Universidad Nacional Autónoma de México, under the auspices of the Interdepartmental Committee on Scientific and Cultural Cooperation, Department of State."