Hassen Abdulahi, Ed Sarobol, Vichan Vichukit, and Chairerk Suwannarat. “Uptake and Response of Maize (Zea Mays L.) Varieties to Nitrogen and Phosphorus Fertilizers in Semi-Arid Areas of Eastern Ethiopia”. Agriculture and Natural Resources, vol. 40, no. 3, June 2006, pp. 604-15, https://li01.tci-thaijo.org/index.php/anres/article/view/243711.