Di, H., and Y. Shang. “Existence, Nonexistence and Decay Estimate of Global Solutions for a Viscoelastic Wave Equation With Nonlinear Boundary Damping and Internal Source Terms”. European Journal of Pure and Applied Mathematics, vol. 10, no. 4, July 2017, pp. 668-01, https://ejpam.com/index.php/ejpam/article/view/3003.