Analysis of Finite Element Methods for Second Order Boundary Value Problems Using Mesh Dependent Norms. L. Babuska; J. Osborn — 1980 Numerische Mathematik
Error estimates for mixed methods R. S. Falk; J. E. Osborn — 1980 ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique