1. Amann, H.: Saddle points and multiple solutions of differential equations. Math. Z. 169, 127–166 (1979)
2. Arcoya, D., Ruiz, D.: The Ambrosetti-Prodi problem for the p-Laplace operator. Commun. Partial Differ. Equ. 31, 349–365 (2006)
3. Bai, Y.: Existence of solutions to nonhomogeneous Dirichlet problems with dependence on the gradient. Electron. J. Qual. Theory Differ. Equ. 2018, 101, 18 pp. (2018)
4. Bai, Y., Gasinski, L., Papageorgiou, N.S.: Nonlinear Dirichlet problems with the combined effects of singular and convection terms. Electron. J. Qual. Theory Differ. Equ. 2019, 57, 13 pp. (2019)
5. Bai, Y., Gasinski, L., Winkerl, P., Zeng, S.: W1, p versus C1: the nonsmooth case involving critical growth. Bull. Math. Sci. 10, 2050009 (2020)