@article{ASNSP_1981_4_8_4_647_0,
     author = {Rabinowitz, Paul H.},
     title = {On nontrivial solutions of a semilinear wave equation},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {647--657},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 8},
     number = {4},
     year = {1981},
     mrnumber = {656003},
     zbl = {0484.35012},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1981_4_8_4_647_0/}
}