1. Multiple nontrivial solutions of resonant and nonresonant asymptotically linear problems;Ahmad,1986
2. Saddle points and multiple solutions of differential equations;Amann;Math. Z.,1979
3. Nontrivial solutions for a class of nonresonance problems and applications to nonlinear differential equations;Amann;Ann. Scuola Norm. Sup. Pisa Cl. Sci. (4),1980
4. Existence and multiplicity results for nonlinear elliptic problems with linear part at resonance;Ambrosetti;J. Differential Equations,1978
5. Theorems of existence and multiplicity for nonlinear elliptic problems with noninvertible linear part;Ambrosetti;Ann. Scuola Norm. Sup. Pisa Cl. Sci. (4),1978