Papageorgiou, N. S., Santos, S. R. A., & Staicu, V. (2010). Nontrivial solutions for nonvariational quasilinear Neumann problems. Topological Methods in Nonlinear Analysis, 36(1), 39–59. Retrieved from https://apcz.umk.pl/TMNA/article/view/TMNA.2010.027