Classification of isolated singularities for nonhomogeneous operators in divergence form

Consider the equation div(φ(|∇u|)|∇u|∇u)=0 on the punctured unit ball from RNRN (N≥2N≥2), where φ   is an odd, increasing homeomorphism from RR onto RR of class C1C1. Under reasonable assumptions on φ we prove that if u is a non-negative solution of our equation, then either 0 is a removable singularity of u or u behaves near 0 as the fundamental solution of the equation investigated here. In particular, our result complements to the case on nonhomogeneous operators in divergence form Bôcher's Theorem and some classical results by Serrin.