1. P. S. Laplace:Traité de Mécanique Céleste, Vol.1 (Villars, Paris, 1799).
2. H. Goldstein:Am. J. Phys.,43, 735 (1975);44, 1123 (1976).
3. C. Runge:Vector Analysis, Vol.1 (Hirzel, Leipzig, 1919), p. 70.
4. W. Lenz:Z. Phys.,24, 197 (1924).
5. For example,H. Goldstein:Classical Mechanics, 2nd edition (Addison-Wesley, Reading, Mass., 1980), p. 102.