1. Böhmer, K.: Asymptotic expansions for the discretization error in linear elliptic boundary value problems on general regions. Math. Z.177, 235?255 (1981)
2. Bramble, J.H., Thomée, V.: Interior maximum norm estimates for some simple finite element methods. RAIRO Anal. Numer.8, 5?18 (1974)
3. Collatz, L.: The Numerical Treatment of Differential Equations. Berlin, Heidelberg, New York: Springer 1966
4. Frehse, J., Rannacher, R.: EineL 1-Fehlerabschätzung für diskrete Grundlösungen in der Methode der finiten Elemente. Bonn. Math. Schr.89, 92?114 (1976)
5. Levine, N.: Pointwise logarithm-free error estimates for finite elements on linear triangles. Numerical Analysis Report Nr. 6, Department of Mathematics, University of Reading 1984