H. Clark, Global classical solutions to the Cauchy problem for a nonlinear wave equation, International Journal of Mathematics and Mathematical Sciences, vol.21, issue.3, pp.533-548, 1998.
DOI : 10.1155/S016117129800074X

L. A. Medeiros, J. Limaco, and S. B. Menezes, Vibrations of Elastic String: Mathematical Aspects, Part one, J. Comput. Anal. Appl, vol.4, issue.2, pp.91-127, 2002.

L. A. Medeiros, J. Limaco, and S. B. Menezes, Vibrations of Elastic String: Mathematical Aspects, Part two, J. Comput. Anal. Appl, vol.4, issue.3, pp.211-263, 2002.

G. P. Menzala, On global classical solutions of a nonlinear wave equation, Applicable Analysis, vol.25, issue.3, pp.179-195, 1980.
DOI : 10.1080/00036818008839300

N. T. Long and A. P. Dinh, On the quasilinear wave equation: utt ??? ??u + f(u, ut) = 0 associated with a mixed nonhomogeneous condition, Nonlinear Analysis: Theory, Methods & Applications, vol.19, issue.7, pp.613-623, 1992.
DOI : 10.1016/0362-546X(92)90097-X

N. T. Long and V. G. Giai, Existence and asymptotic expansion for a nonlinear wave equation associated with nonlinear boundary conditions, Nonlinear Anal. Series A: Theory and Methods, pp.1791-1819, 2007.

M. L. Santos, Decay rates for solutions of a system of wave equations with memory, EJDE, vol.2002, issue.38, pp.1-17, 2002.