Figure 1: Periodic change of the chaotic attractor of the Duffing oscillator for \(\alpha=1\ ,\) \(\beta=-1\ ,\) \(\delta=0.2\ ,\) \(\gamma=0.3\ ,\) and \(\omega=1\ .\) By assembling the Poincaré sections of a trajectory for different phase \(\psi \equiv \omega t \mbox{ mod } 2 \pi\ ,\) the attractor of Duffing oscillator changes periodically (see also Figure 1). Duffing oscillator is an example o