The common way to improve properties of the Galerkin finite element discretization of a convection-diffusion-reaction problem is to modify the variational form, e.g., by changing the definition of some of the bilinear forms or by adding additional terms, as it was discussed in the previous chapters. However, it is also possible to modify directly the linear algebraic system corresponding to the Galerkin finite element discretization, which will be pursued in this chapter. To obtain accurate approximate solutions, these algebraic modifications have to be defined in a nonlinear way.