1. Babu?ka, I., Aziz, A.K.: Survey lectures on the mathematical foundations of the finite element method. In: The Mathematical Foundations of the Finite Element Method with Application to Partial Differential Equations (A.K. Aziz, ed.), pp. 3?359. New York, London: Academic Press 1972
2. Brebbia, C.A.: The Boundary Element Method for Engineering. London: Pentch Press 1978
3. Ciarlet, P.G.: The Finite Element Method for Elliptic Problem. Amsterdam, New York, Oxford: North Holland 1978
4. Courant, R., Hilbert, D.: Methods of Mathematical Physics. Vol. 1. New York: Interscience 1953
5. Delves, L.M., Hall, C.A.: An implicit matching principle for global element calculation. J. Inst. Math. Appl.23, 223?234 (1979)