EN
We consider the Neumann problem for the equation $-Δu - λu = Q(x)|u|^{2*-2}u$, u ∈ H¹(Ω), where Q is a positive and continuous coefficient on Ω̅ and λ is a parameter between two consecutive eigenvalues $λ_{k-1}$ and $λ_{k}$. Applying a min-max principle based on topological linking we prove the existence of a solution.