J. Cea, D. Chenais, G. Geymonat, and J. Lions (Eds.) volume 22 of Progress in Nonlinear Differential Equations and Their Applications, Boston, Birhäuser, (1996)
M. Dauge, S. Nicaise, M. Bourlard, and J. Lubuma. ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique, 24 (1):
27--52(1990)