1. For general information, seeJ. Moser:Stable and Random Motions in Dynamical Systems (Princeton, 1973);R. Helleman:Self-generated chaotic behaviour in nonlinear mechanics, inFundamental Problems in Statistical Mechanics, Vol.5, edited byE. G. D. Cohen (Amsterdam, 1980);Dynamical Systems and Chaos, Proceedings Sitges 1982, edited byL. Garrido (Berlin, 1983).
2. M. Casartelli:Phys. Rev. A,19, 1741 (1979).
3. M. Casartelli, E. Diana, L. Galgani andA. Scotti:Phys. Rev. A,13, 1921 (1976);G. Casati:Theor. Math. Phys.,29, 1022 (1977).
4. P. Bocchieri, A. Scotti, B. Bearzi andA. Loinger:Phys. Rev. A,2, 2013 (1970).
5. M. Casartelli:Lett. Nuovo Cimento,33, 293 (1982).