http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Secretaría de la Defensa Nacional, Departamento Cartográfico Militar ; printed by Army Map Service Corps of Engineers.
Relief shown by contours and spot heights.
Sheets numbered NG 12-2; NH 11-3; NH 12-1; NI 12-10, etc.