1. Nonlinear perturbations of linear elliptic and parabolic problems at resonance: existence of multiple solutions;Hess;Ann. Scu. norm. sup., Pisa,1978
2. Remarks on some nonlinear boundary value problems;Fučik;Commentat. math. Univ. Carol.,1976
3. Existence and multiplicity results for nonlinear elliptic problems with linear part at resonance;Ambrosetti;J. diff. Eqns,1978
4. Theorems of existence and multiplicity for nonlinear elliptic problems with non-invertible linear part;Ambrosetti;Ann. Scu. norm. sup., Pisa,1978
5. Boundary value problems with bounded nonlinearity and general nullspace of the linear part;Fučik;Math. Z.,1977