Nonlinear Elliptic Boundary Value Problems at Strong Resonance
Martin Schechter · American Journal of Mathematics · 1990
Let A be a linear elliptic partial differential operator on a domain Ω⊂R n such that the boundary value problem (1.1) Au=λu in Ω, Bu=0 on ∂Ω is selfadjoint and has a discrete set of isolated eigenvalues bounded from below and no other spectrum