1. W.F. Ames: Numerical Methods for Partial Differential Equations (Nelson,London 1969)
2. A.G.A.M. Armstrong, C.J. Collie, N.J. Diserens, M.J. Newman, J. Simkin, C.W. Trowbridge: Proc. 5th Int. Conf. Magnet Technology, Rome, 1975, ed. by N. Sacchetti, M. Spadoni, S. Stipcich ( Laboratori Nazionali del CNEN, Frascati 1975 ) pp. 168–182
3. K.A. Aziz: The Mathematical Foundations of the Finite Element Method with Applications to Partial Differential Equations(Academic, New York, London 1972 )
4. Buneman: “A Compact Non-Iterative Poisson Solver”, Report 294, Stanford University, California (1969)
5. J.W. Butler: Proc. 6th Int. Cong. Electron Microscopy, Kyoto, 1966, Vol.I, ed. by R. Uyeda ( Maruzen Co., Tokyo 1966 ) pp. 191–192