Error analysis Anisotropic finite elements Cuspidal domains Finite element method Graded meshes Neumann problem Anisotropic elements Discontinuous Galerkin methods Finite elements Numerical methods Regularity Traces Weighted norms Convection-diffusion Discontinuous galerkin Error estimates Galerkin methods Interpolation Linear equations Mathematical models Mixed finite elements Perturbation techniques Problem solving Superconvergence A posteriori estimator Advection Advection diffusion equation Advection-diffusion equations Anisotropic hybrid meshes Approximation algorithms