References
- Adams R. 1975 Sobolev Spaces Academic Press New York
- Castro , A. and Lazer , A.C. 1976 . A minmax principle and applications . Revista Colombiana de Matematicas , X : 141 – 149 .
- Castro , A. and Lazer , A.C. 1979 . Critical point theory and the number of solutions of a nonlinear Dirichlet problem . Annli di Mat. Pura ed Applicata (IV) , CXX : 113 – 137 .
- Fernandez , L. and Zanolin , F. 1988 . Periodic solutions of a second order differential equation with one-sided growth restriction on the restoning term . Arch. Math. , 51 : 151 – 163 .
- Hofer H. 1986 The topological degree at a critical point of mountain pass type Proceedings of Symposia in Pure Mathematics Part I 45
- Fucik , S. 1976 . Boundary value problems with jumping nonlinearities . Casopis Pest. Mat. , 101 : 69 – 87 .
- Rabinowitz P. 1986 Minimax methods in critical point theory with applications to differential equations Regional Conference Series in Mathematics 65 Providence, R.I.