Dragunov, D. V., Makarov, V. L., & Sember, D. A. (2012). FD-method for solving the nonlinear Klein - Gordon equation. Ukrains’kyi Matematychnyi Zhurnal, 64(10), 1394-1415. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/2667