  The particular properties of synchronization are discussed for coupled
auto-oscillating systems, which are characterized by non-quadratic law of
potential dependence on the coordinate. In particular, structure of the
parameter plane (frequency mismatch - coupling value) is considered for coupled
van der Pol - Duffing oscillators. The arrangement of synchronization tongues
and the particular properties of their internal structure in the parameter
space are revealed. The features of attractors in the phase space are
discussed.
