1. Castro, A.: Hammerstein integral equations with indefinite kernel. Int. J. Math. Math. Sci. 1, 187–201 (1978)
2. Castro, A., Chang, C.: A variational characterization of the Fučík Spectrum and applications. Rev. Colomb. Mat. 44(1), 23–40 (2010)
3. Cuesta, M., de Figueiredo, D., Gossez, J.-P.: The beginning of the Fučík Spectrum for the p-Laplacian. J. Differ. Equ. 159, 212–238 (1999)
4. de Figueiredo, D., Gossez, J.-P.: On the first curve of the Fučík Spectrum of an elliptic operator. Differ. Integral Equ. 7(5–6), 1285–1302 (1994)
5. Drábek, P., Robinson, S.: A variational characterization of the Fučík Spectrum. Abstr. Appl. Anal. 2010, Article ID 125464 (2010)