1. Aizicovici, S., Papageorgiou, N., Staicu, V.: Degree Theory for Operators of Monotone Type and Nonlinear Elliptic Equations with Inequality Constraints, vol. 196. Memoirs Amer. Math. Soc, Providence (2008)
2. Ambrosetti, A., Brezis, H., Cerami, G.: Combined effects of concave and convex nonlinearities in some elliptic problems. J. Funct. Anal. 122, 519–543 (1994)
3. Ambrosetti, A., Rabinowitz, P.: Dual variational methods in critical point theory and applications. J. Funct. Anal. 14, 349–381 (1973)
4. Brezis, H., Nirenberg, L.:
$$H^1$$
H
1
versus
$$C^1$$
C
1
local minimizers. C. R. Acad. Sci. Paris Sér. I 317, 465–472 (1993)
5. Cuesta, M.: Eigenvalue problems for the
$$p$$
p
-Laplacian with indefinite weights. Electron. J. Differ. Equ. 2001(33), 1–9 (2001)