1. Agarwal, G. S. and Wolf, E. (1970).Physical Review,D2, 2161.
2. Ahrens, R. & Babitt, D. (1965).Journal of Mathematical Physics,6, 1071.
3. Arnold, V. J. and Avez, A. (1967).Problèmes Ergodiques de la Mécanique Classique. Gauthier-Villars, Paris.
4. Chevalley, C. (1954).The Construction and Study of Certain Important Algebras. Mathematical Society of Japan, Tokio.
5. Falk, G. (1953).Zeitschrift für Physik,135, 431.