@article{ASNSP_1980_4_7_4_539_0,
     author = {Amann, H. and Zehnder, E.},
     title = {Nontrivial solutions for a class of nonresonance problems and applications to nonlinear differential equations},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {539--603},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 7},
     number = {4},
     year = {1980},
     mrnumber = {600524},
     zbl = {0452.47077},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_1980_4_7_4_539_0/}
}