@article{ASNSP_1978_4_5_3_527_0,
     author = {Hess, Peter},
     title = {Nonlinear perturbations of linear elliptic and parabolic problems at resonance : existence of multiple solutions},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {527--537},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 5},
     number = {3},
     year = {1978},
     mrnumber = {506999},
     zbl = {0392.35051},
     language = {en},
     url = {http://archive.numdam.org/item/ASNSP_1978_4_5_3_527_0/}
}