  A nonadditive generalization of Klimontovich's S-theorem [G. B. Bagci, Int.J.
Mod. Phys. B 22, 3381 (2008)] has recently been obtained by employing Tsallis
entropy. This general version allows one to study physical systems whose
stationary distributions are of the inverse power law in contrast to the
original S-theorem, which only allows exponential stationary distributions. The
nonadditive S-theorem has been applied to the modified Van der Pol oscillator
with inverse power law stationary distribution. By using nonadditive S-theorem,
it is shown that the entropy decreases as the system is driven out of
equilibrium, indicating self-organization in the system. The allowed values of
the nonadditivity index $q$ are found to be confined to the regime (0.5,1].
