Nizhnik, L. P. “Stable Difference Scheme for a Nonlinear Klein-Gordon Equation”. Ukrains’kyi Matematychnyi Zhurnal 49, no. 6 (June 25, 1997): 857–859. Accessed April 14, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5073.