1. E. Jahnke and F. Emde, Funktionentafeln mit Formeln und Kurven, 3rd ed., Leipzig and Berlin, 1938; 4th ed., New York, 1945.
2. W. E. Milne, Numerical Calculus, Princeton, 1949.
3. L. M. Milne-Thompson, The Calculus of Finite Differences, London, 1933.
4. D. A. Murray, Introductory Course in Differential Equations, New York, 1897.