Under sole qualitative hypotheses in the large the author has proved the existence of equibounded solutions to nonlinear operational equations in a Hilbert space when a parameter describes an interval containing a point of resonance. Applications have been made to problems of periodic solutions, and to elliptic problems.
@article{RLINA_1976_8_60_3_198_0, author = {Lamberto Cesari}, title = {Teoremi di esistenza al passaggio attraverso valori critici}, journal = {Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti}, volume = {60}, year = {1976}, pages = {198-201}, zbl = {0364.47029}, mrnumber = {0493556}, language = {it}, url = {http://dml.mathdoc.fr/item/RLINA_1976_8_60_3_198_0} }
Cesari, Lamberto. Teoremi di esistenza al passaggio attraverso valori critici. Atti della Accademia Nazionale dei Lincei. Classe di Scienze Fisiche, Matematiche e Naturali. Rendiconti, Tome 60 (1976) pp. 198-201. http://gdmltest.u-ga.fr/item/RLINA_1976_8_60_3_198_0/
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