A general approach to solvability conditions for semilinear elliptic boundary value problems at resonance
The authors show how many well-known existence theorems and several new existence theorems for semilinear elliptic boundary value problems at resonance can be viewed as simple corollaries of some abstract existence results. The abstract existence theorems are derived by using the Leray- Schauder degree theory and the approximate domain technique (for unbounded domains).
scientific article; zbMATH DE number 763482