BoikoV. M., and FushchichV. I. “Galilei-Invariant Higher-Order Equations of Burgers and Korteweg-De Vries Types”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 48, no. 12, Dec. 1996, pp. 1589-01, https://umj.imath.kiev.ua/index.php/umj/article/view/5182.