(color online) Fitness value curves and output of system with different reference signals: Panels (a) and (b) are fitness value curve and output of Sinusodial chaotic system with constant signal. Panels (c) and (d) are fitness value curve and output of sinusodial chaotic system with sinusoidal signal. Panels (e) and (f) are fitness value curve and output of sinusodial chaotic system with square signal. Panels (g) and (h) are fitness value curve and output of sinusodial chaotic system with sawtooth signal.