Adeyinka Olubunmi, Makinde, A.A, and gideon ufoegbune. 2012. “Application of Rainfall- Potential Evapotranspiration Model for Determining Optimum Planting Date of Yam (Dioscorea Rotundata) in a Tropical Wet-and-Dry Climate”. Global Journal of Science Frontier Research 12 (D5):53-58. https://journalofscience.org/index.php/GJSFR/article/view/515.