James E. Brady, Joseph W. Ball, Ronald L. Bishop, Duncan C. Pring, Norman Hammond and Rupert A. Hou. "The Lowland Maya Protoclassic: A reconsideration of its nature and significance." Ancient Mesoamerica 9/1 (March 1998): 17-38.

James E. Brady, Joseph W. Ball, Ronald L. Bishop, Duncan C. Pring, Norman Hammond and Rupert A. Hou. "The Lowland Maya Protoclassic: A reconsideration of its nature and significance." Ancient Mesoamerica 9/1 (March 1998): 17-38.