Kenneth M. Olsen and Barbara A. Schaal (1999). “Evidence on the origin of cassava: Phylogeography ofManihot esculenta” . Proceedings of the National Academy of Sciences 96 (10): 5587, 5590. doi : 10.1073/pnas.96.10.5586 . https://doi.org/10.1073/pnas.96.10.5586 . Kevin O. Pope and Mary E. D. Pohl a...