Mixed finite-element approximations of linear boundary-value problems Academic Article

A theory of mixed finite-element/Galerkin approximations of a class of linear boundary-value problems of the type T T u + k u + f = 0 T*Tu + ku + f = 0 is presented, in which appropriate notions of consistency, stability, and convergence are derived. Some error estimates are given and the results of a number of numerical experiments are discussed.