Finite element approximation of a free boundary problem arising in the theory of liquid drops ans plasma physics John W. Barrett; Charles M. Elliott — 1991 ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique
Finite Element Approximation of the Dirichlet Problem Using the Boundary Penalty Method. John W. Barrett; Charles M. Elliott — 1986 Numerische Mathematik
A Practical Finite Element Approximation of a Semi-Definite Neumann Problem on a Curved Domain. John W. Barrett; Charles M. Elliott — 1987 Numerische Mathematik