1. Teubner-Texte zur Mathematik;O. Axelsson,1984
2. Axelsson, O., Eijkhout, V., Polman, B., Vassilevki, P. (1987): Iterative solution of singular perturbation second order boundary value problems by use of incomplete block-matrix factorization methods. Cath. Univ. Nijmegen, Report 8709
3. Bagaev, B.M. (1986): Solution of a parabolic equation with a small parameter multiplying the time derivative [Russ.]. ?isl. Met. Mech. Splo?n Sredy17, 13?26
4. Boccardo, L., Murat, L., Puel, J.P. (1988): Quelques proprietes des operateurs elliptiques quasi lineaires, C.R.A.S., t.307, Ser. I, 749?752
5. Ciarlet, P. (1978): The Finite Element Method for Elliptic Problems. North Holland, Amsterdam