  We obtain entropy formulas for SRB measures with finite entropy given by
inducing schemes. In a first part, we deduce the entropy formula for a class of
systems whose SRB measures are given by Gibbs-Markov induced maps. In a second
part, the entropy formula is derived for SRB measures given by Young sets,
taking into account a classical compression technique along the stable
direction that allows a reduction of the return map associated with a Young set
to a Gibbs-Markov map. In both situations, we give applications of our main
results to several classes of dynamical systems with singular sets, where the
classical results by Ruelle and Pesin cannot be applied directly. We also
present examples for which Ruelle inequality does not hold.
