Philip Drucker and Eduardo Contreras, "Site Patterns in the Eastern Part of Olmec Territory," Journal of the Washington Academy of Sciences 43 (1953):392-93; Thomas A. Lee, Jr., "The Historical Routes of Tabasco and Northern Chiapas and Their Relationship to Early Cultural Developments in Central Chiapas," in Mesoamerican Communication Routes and Cultural Contacts, ed. Thomas A. Lee, Jr., and Carlos Navarrete, NWAF 40 (1978), p. 54.