Schele, Linda, and Peter Mathews. 1998. The Code of Kings: The Language of Seven Sacred Maya Temples and Tombs. New York: Scribner: 8:47, Fig. 1.22e;
Freidel, David A., Linda Schele, and Joy Parker. 1993. Maya Cosmos: Three Thousand Years on the Shaman's Path. New York: W. Morrow: 196, Fig. 4:11c