Schele, Linda. 1995. "The Olmec mountain and Tree of Creation in Mesoamerican Cosmology". Olmec World : Ritual and Rulership: 5:111, Fig. 16a
Freidel, David A., Linda Schele, and Joy Parker. 1993. Maya Cosmos: Three Thousand Years on the Shaman's Path. New York: W. Morrow: 89, Fig. 2:24