The standard Galerkin method -- Semidiscrete methods based on more general approximations of the elliptic problem -- Smooth and non-smooth data error estimates for the homogeneous equation -- Parabolic equations with more general elliptic operators -- Maximum-Norm estimates -- Negative norm estimates and superconvergence -- Completely discrete schemes for the homogeneous equation -- Completely discrete schemes for the inhomogeneous equation -- Time discretization by the discontinuous Galerkin method -- A nonlinear problem -- The method of lumped masses -- The H1 and H?1 methods -- A mixed method -- A singular problem