Ibragimov, N.H., M. Torrisi, and R. Tracin 'a. “Some Results About Self-Adjointness of a Class of Nonlinear Wave Equations”. Journal of Vibration Testing and System Dynamics 5, no. 3 (August 17, 2026): 279–283. Accessed August 17, 2026. https://lhscientificpublishing.com/index.php/jvtsd/article/view/169.