[1] J. P. Aubin: 
Approximation of elliptic boundary value problems. Wiley-Interscience (1972). 
MR 0478662 | 
Zbl 0248.65063 
[2] I. Babuška J. E. Osborn: 
Generalized finite element methods: their performance and their relation to mixed methods. SIAM J. Numer. Anal. 20 (1983), 510-536. 
DOI 10.1137/0720034 | 
MR 0701094 
[4] P. Ciarlet: 
The finite element method for elliptic  problems. North-Holland  Publishing Company (1978). 
MR 0520174 | 
Zbl 0383.65058 
[5] C. A. Chandler: 
Superconvergence for second kind integral equations, Application and Numerical Solution of Integral Equations. Sijthoff, Noordhoff (1980), 103-117. 
MR 0582986 
[6] P. J. Dams: Interpolation and approximation. Blaisdell Publishing Company (1963).
[7] J. Douglas, Jr. T. Dupont: 
Some superconvergence results for Galerkin methods for the approximate solution of two point boundary problems. Topics in numerical analysis, (1973), 89-92. 
MR 0366044 
[8] J. Douglas, Jr. T. Dupont: 
Collocation methods for parabolic equations in a single space variable. Lecture Notes in Math. 385 (1974). 
MR 0483559 
[9] T. Dupont: 
A unified theory of superconvergence for Galerkin methods for two-point boundary value problems. SIAM J. Numer. Anal. vol. 13, no. 3, (1976), 362-368. 
DOI 10.1137/0713032 | 
MR 0408256 
[11] T. Regińska: 
Superconvergence of external approximation for two-point boundary problems. Apl. Mat. 32 (1987), pp. 25-36. 
MR 0879327 
[13] A. Spence K. S. Thomas: 
On superconvergence properties of Galerkin's method for compact operator equations. IMA J. Numer. Anal. 3 (1983), pp. 253 - 271. 
DOI 10.1093/imanum/3.3.253 | 
MR 0723049 
[14] V. Thomée: 
Spline approximation and difference schemes for the heat equation. The mathematical foundations of finite element method with application to partial differential equations. Academic Press (1972), pp. 711 - 746. 
MR 0403265