Al-Ashor, A. A. M. “Interaction Effect of Phosphorus and Zinc Fertilizer for Different Levels in Growth of Two Varieties of Wheat Plant”. Ibn AL-Haitham Journal For Pure and Applied Sciences, vol. 23, no. 1, May 2017, pp. 117-29, https://jih.uobaghdad.edu.iq/index.php/j/article/view/983.