@article{ASNSP_1990_4_17_4_569_0,
     author = {Coti Zelati, Vittorio and Ekeland, Ivar and Lions, Pierre-Louis},
     title = {Index estimates and critical points of functionals not satisfying {Palais-Smale}},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {569--581},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 17},
     number = {4},
     year = {1990},
     mrnumber = {1093709},
     zbl = {0725.58019},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1990_4_17_4_569_0/}
}