Error estimates in balanced norms of finite element methods on Shishkin   meshes for reaction-diffusion problems
  Error estimates of finite element methods for reaction-diffusion Problems are often realized in the related energy norm. In the singularly perturbed case, however, this norm is not adequate. A different scaling of the $H^1$ seminorm leads to a balanced norm which reflects the layer behavior correctly. We discuss also anisotropic problems, semilinear equations, supercloseness and a combination technique. 
Hans-Goerg Roos
math.NA