SamoilenkoV. G., and SamoilenkoYu. I. 2005. “Asymptotic Expansions for One-Phase Soliton-Type Solutions of the Korteweg-De Vries Equation With Variable Coefficients”. Ukrains’kyi Matematychnyi Zhurnal 57 (1), 111–124. https://umj.imath.kiev.ua/index.php/umj/article/view/3578.