1. Cacao use and the San Lorenzo Olmec
2. Powis Terry G. 2007 An Archaeological Investigation of the Origins of Cacao Drinking: The Ceramic Evidence from the Gulf Coast and Pacific Coast of México. Foundation for Ancient Mesoamerican Studies, Incorporated (FAMSI). Electronic document, http://www.famsi.org/reports/06047/index.html, accessed August 6, 2013.
3. The Way of God L: The Princeton Vase Revisited;Kerr;Record of the Princeton Art Museum,2005