1. Al-Idrisi. 1154. Description de l’Afrique et de l’Espagne. (Transl, by R. P. A. Dozy and M. J. de Goeje. 1969). Oriental Press, Amsterdam.
2. Baker, H. G. 1962. Comments on the thesis that there was a major centre of plant domestication near the headwaters of the river Niger. J. Afr. Hist. 3:229–233.
3. Bilquez, A. F., and J. Lecomte. 1969. Relations entre mils sauvages et mils cultives: etude l’hybridePennisetum typhoides Stapf & Hubb. XP. violaceum (Lam.) L. Rich. Agron. Trop.24:249–257.
4. Ph.D. Dissertation;J. N. Brunken,1975
5. Butzer, K. W. 1966. Climatic changes in the arid zone of Africa during early mid-Holocene times. In World Climate from 8000 to 0 B.C. Royal Metrological Inst., London.