or the case of frequency ratio 0.0000, parameter *u* has three equilibrium points when parameter *d* = 0.00; for the case of frequency ratio 0.0000, parameter *u* has three equilibrium points when parameter *d* = 0.000 and 0.000; for the case of frequency ratio 0.0000, parameter *u* has three equilibrium points when parameter *d* = 0.000 and 0.000