Carrasco, Pedro. "Central Mexican Highlands: Introduction." In Ethnology, edited by Robert Wauchope and Evon Z. Vogt, 579. Vols. 7-8 of Handbook of Middle American Indians. Austin: University of Texas Press, 1969. https://ebookcentral-proquest-com.proxy.library.upenn.edu/lib/upenn-ebooks/reader.action?docID=4826335&ppg=600.