Question: bifurcation

How could I plot bifurcation for a nonlinear system using maple? For example I have the following nonlin. syst: x'=a*b*((x^2+c^2)/(x^2+1))-d*x y'=a*e*((y^3+f^3)/(x^3+1)*(g*x+1)-y for a, b c, d, e, f,g be given ; I want to get bifurcation by some parameter, e for instance. An example: for a=7, b=1.4, c=0.2, d=0.1, e=12, f=0.5 and g=2.8 I obtain only one equilibria point, namely an atractor. Futhermore, for different values of e betwen 0.1 and 2, I always get one stable point, so a hypebolic one. This really means thai I have no bifurcation by e? For plotting bifurcation I should have at least nonhyperbolic critical point? How could I get it? Please help me! Thanks!
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