Samoilenko, V. G., & Samoilenko, Y. I. (2012). Asymptotic m-phase soliton-type solutions of a singularly perturbed Korteweg?de Vries equation with variable coefficients. Ukrains’kyi Matematychnyi Zhurnal, 64(7), 970-87. https://umj.imath.kiev.ua/index.php/umj/article/view/2632