  We prove the existence of Sinai-Ruelle-Bowen measures for a class of $C^2$
self-mappings of a rectangle with unbounded derivatives. The results can be
regarded as a generalization of a well-known one dimensional Folklore Theorem
on the existence of absolutely continuous invariant measures. In an earlier
paper analogous results were stated and the proofs were sketched for the case
of invertible systems. Here we give complete proofs in the more general case of
noninvertible systems, and, in particular, develop the theory of stable and
unstable manifolds for maps with unbounded derivatives.
