The shaded region in the picture is bounded by the stable and
unstable manifold segments of the fixed points and contains the
invariant set. Let 
denote a
boundary point that is not on the stable manifold of any of the fixed points.
D
() is a small disk of radius centered at ,
and L() is a horizontal line segment through contained in D(). For a sufficient number of iterates m,
fm(L()) will cross segments of the stable manifold bounding
the shaded region.
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