(color online) Analytically obtained two-parameter bifurcation diagram showing the synchronization dynamics of the parallel LCR circuit with a simplified nonlinear element in the –f₁ plane: (a) the amplitude of the response system is fixed at f₂= 0.695, (b) the amplitude of the response system is fixed at f₂ = 0.855. The synchronization dynamics is color-coded as follows: red-unsynchronized state (US), green-complete synchronization state (CS), and blue-phase synchronized state (PS).