Robust exponential convergence of hp-FEM in balanced norms for   singularly perturbed reaction-diffusion problems: corner domains
  The hp-version of the finite element method is applied to singularly perturbed reaction-diffusion type equations on polygonal domains. The solution exhibits boundary layers as well as corner layers. On a class of meshes that are suitable refined near the boundary and the corners, robust exponential convergence (in the polynomial degree) is shown in both a balanced norm and the maximum norm. 
Jens Markus Melenk and Markus Faustmann
math.NA