Boonruangkan, N., A. Chaiworn, W. Sanprasert, and P. Chansangiam. “Stationary Iterative Methods and the Conjugate Gradient Method for Solving Linear Systems”. Science Essence Journal, vol. 35, no. 2, Aug. 2019, pp. 177-92, https://ejournals.swu.ac.th/index.php/sej/article/view/10647.