Madeiros, L.A., and Manuel Milla Miranda. “On a Nonlinear Wave Equation With Damping”. Revista Matemática Complutense 3, no. 2 (January 1, 1990): 213. Accessed August 1, 2026. https://revistas.ucm.es/index.php/REMA/article/view/REMA9090220213A.