Ratananikom, W., and S. Yimsiri. “Simplified Method for Analyzing Slope Stability of Clay Layer of Increasing Strength With Depth”. Frontiers in Engineering Innovation Research, vol. 21, no. 2, Dec. 2023, pp. 57-68, https://ph01.tci-thaijo.org/index.php/jermutt/article/view/253277.