Local superconvergence analysis of the approximate boundary-flux calculation Lazarov, R. D.; Pehlivanov, A. I. — 1990 Equadiff 7
Error estimates for least-squares mixed finite elements A. I. Pehlivanov; G. F. Carey — 1994 ESAIM: Mathematical Modelling and Numerical Analysis - Modélisation Mathématique et Analyse Numérique