Lecturas recomendadas

--> David E. Duncan. Calendar: Humanity´s Epic Struggle to Determine a True and Accurate Year, AVON books, EEUU, 1998.

--> Peter Schmidt, De la Garza M. y E. Nalda. Los mayas. Coedición CNCA-INAH, México, 1998.

--> Daniel J. Boosrtin. The Discoverers: A History of Man´s Search to know his World and Himself. Random House, EEUU, 1983.