BarannykT. A., BarannykA. F., and YurykI. I. 2010. “Generalized Separation of Variables and exact solutions of Nonlinear Equations”. Ukrains’kyi Matematychnyi Zhurnal 62 (12), 1598 - 1609. https://umj.imath.kiev.ua/index.php/umj/article/view/2985.