@article{MZ_1962__80_170102,
     author = {Felix E. Browder},
     title = {On {Non-Linear} {Wave} {Equations.}},
     journal = {Mathematische Zeitschrift},
     pages = {249--264},
     year = {1962},
     volume = {80},
     zbl = {0109.32102},
     url = {http://geodesic.mathdoc.fr/item/MZ_1962__80_170102/}
}