Discrete forms of Friedrichs' inequalities in the finite element method Alexander Ženíšek (1981) ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique
Discrete Sobolev spaces and regularity of elliptic difference schemes Rob Stevenson (1991) ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique