Abdalla, O. A., E. A. Mohamed, A. M. E. . Naim, M. A. E. . Shiekh, and M. B. Zaied. “Effect of Disc and Tilt Angles of Disc Plough on Tractor Performance under Clay Soil”. Current Research in Agricultural Sciences, vol. 1, no. 3, Sept. 2014, pp. 83-94, https://archive.conscientiabeam.com/index.php/68/article/view/63.