Global existence and non-existence theorems for nonlinear wave equations David PittsMohammad Rammaha 35L0535L2058G16wave equationsdamping and source termsweak solutionsblow-up of solutions Indiana University Mathematics Journal 2002 text pdf 10.1512/iumj.2002.51.2215 10.1512/iumj.2002.51.2215 en Indiana Univ. Math. J. 51 (2002) 1479 - 1510 state-of-the-art mathematics http://iumj.org/access/