  Dynamics of the Duffing--Van der Pol driven oscillator is investigated.
Periodic steady-state solutions of the corresponding equation are computed
within the Krylov-Bogoliubov-Mitropolsky approach to yield dependence of
amplitude $A$ on forcing frequency $\Omega $ as an implicit function, $F\left(
A,\Omega \right) =0$, referred to as resonance curve or amplitude profile.
  In singular points of the amplitude curve the conditions $\frac{\partial
F}{\partial A}=0$, $\frac{\partial F}{\partial \Omega }=0$ are fulfilled, i.e.
in such points neither of the functions $A=f\left( \Omega \right) $, $\Omega
=g\left( A\right) $, continuous with continuous first derivative, exists. Near
such points metamorphoses of the dynamics can occur. In the present work the
bifurcation set, i.e. the set in the parameter space, such that every point in
this set corresponds to a singular point of the amplitude profile, is computed.
  Several examples of singular points and the corresponding metamorphoses of
dynamics are presented.
