  In this paper we study the existence, uniqueness and asymptotic stability of
the periodic solutions for a Lipschitz system with a small right hand side.
Classical hypotheses in the periodic case of second Bogolyubov's theorem imply
our ones. By means of the results established we construct the curves of
dependence of the amplitude of asymptotically stable $2\pi$--periodic solutions
of the nonsmooth van der Pol oscillator on the detuning parameter and the
amplitude of the perturbation. After, we compare the resonance curves obtained,
with the resonance curves of the classical van der Pol oscillator which were
first constructed by Andronov and Witt.
