Preceramic maize in Central Panama: Phytolith and Pollen Evidencev. 87No. 4871–877
Piperno, Dolores R., Clary, Karen Husum, Cooke, Richard G., Ranere, Anthony J., and Weiland, Doris. 1985. "Preceramic maize in Central Panama: Phytolith and Pollen Evidence." American Anthropologist, 87, (4) 871–877.