  We present numerical verification of hyperbolic nature for chaotic attractor
in a system of two coupled non-autonomous van der Pol oscillators (Kuznetsov,
Phys. Rev. Lett., 95, 144101, 2005). At certain parameter values, in the
four-dimensional phase space of the Poincare map a toroidal domain (a direct
product of a circle and a three-dimensional ball) is determined, which is
mapped into itself and contains the attractor we analyze. In accordance with
the computations, in this absorbing domain the conditions of hyperbolicity are
valid, which are formulated in terms of contracting and expanding cones in the
tangent spaces (the vector spaces of the small state perturbations).

Chaotic Dynamics