@article{JRAM_1988__391_153069,
     author = {M.A. Rammaha},
     title = {On the blowing up of solutions to nonlinear wave equations in two space dimensions.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {55--64},
     year = {1988},
     volume = {391},
     zbl = {0649.35062},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1988__391_153069/}
}