The geologic age of Valsequillo archaeologic sites. - o.O. enth.: Preliminary report on radiocarbon dates from the Valsequillo area, Puebla, Mexico / C. Irwin-Williams ; H. E. Malde Manuskripte - Malde, Harold E. (Annual Meeting of the Society for American Archaeology <May, 1967, Ann Arbor> : oral report. - 20 S. (11 S.)., 1967)