Patcha, Chanyanit, and Warisa Nakpim. “Linearization of Fourth-order Ordinary Differential Equations by Generalized Sundman Transformations”. KKU Science Journal 46, no. 1 (March 30, 2018): 142–153. accessed April 13, 2025. https://ph01.tci-thaijo.org/index.php/KKUSciJ/article/view/249820.