no. 1
Some critical point theorems and applications to semilinear elliptic partial differential equations
Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 5 (1978) no. 1, pp. 215-223. 
@article{ASNSP_1978_4_5_1_215_0,
     author = {Rabinowitz, Paul-H.},
     title = {Some critical point theorems and applications to semilinear elliptic partial differential equations},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {215--223},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 5},
     number = {1},
     year = {1978},
     zbl = {0375.35026},
     mrnumber = {488128},
     language = {en},
     url = {archive.numdam.org/item/ASNSP_1978_4_5_1_215_0/}
}
Rabinowitz, Paul H. Some critical point theorems and applications to semilinear elliptic partial differential equations. Annali della Scuola Normale Superiore di Pisa - Classe di Scienze, Série 4, Tome 5 (1978) no. 1, pp. 215-223. http://archive.numdam.org/item/ASNSP_1978_4_5_1_215_0/

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