1. Abramowitz M, Stegun IA, editors. Handbook of mathematical functions with formulas, graphs, and mathematical tables. New York: Dover; 1972. p. 361.
2. An introduction to numerical analysis;Atkinson,1989
3. Eigenvalue problems;Babuska,1991
4. Integral operators in the theory of linear partial differential equations;Bergman,1969
5. Numerical solution of elliptic problems;Birkhoff,1984