1. G. M. Zaslavsky, Chaos in Dynamical Systems (Nauka, Moscow, 1984; Harwood Academic, New York, 1985).
2. R. Z. Sagdeev, D. A. Usikov, and G. M. Zaslavsky, Nonlinear Physics: From the Pendulum to Turbulence and Chaos (Harwood Academic, New York, 1988).
3. A. Lichtenberg and M. Lieberman, Regular and Stochastic Motion (Springer, New York, 1983).
4. M. Berry, in Quantum Chaos, Proceedings of the Adriatico Research Conference and Miniworkshop, Trieste, 1990, Ed. by H. Cerdeira, R. Ramaswamy, M. Gutzwiller, and G. Casati (World Sci., Singapore, 1991), p. VII.
5. T. Brody, Lett. Nuovo Cimento 7, 482 (1973).