@article{Aizicovici_Papageorgiou_Staicu_2010, title={Existence and multiplicity of solutions for resonant nonlinear Neumann problems}, volume={35}, url={https://apcz.umk.pl/TMNA/article/view/TMNA.2010.014}, abstractNote={We consider nonlinear Neumann problems driven by the $p$-Laplacian
differential operator with a Caratheodory nonlinearity. Under hypotheses which
allow resonance with respect to the principal eigenvalue $\lambda_{0}$ $=0$ at
$\pm\infty$, we prove existence and multiplicity results. Our approach is
variational and uses critical point theory and Morse theory (critical groups).}, number={2}, journal={Topological Methods in Nonlinear Analysis}, author={Aizicovici, Sergiu and Papageorgiou, Nikolaos S. and Staicu, Vasile}, year={2010}, month={Apr.}, pages={235–252} }