  We consider a large class of piecewise expanding maps T of [0,1] with a
neutral fixed point, and their associated Markov chain Y_i whose transition
kernel is the Perron-Frobenius operator of T with respect to the absolutely
continuous invariant probability measure. We give a large class of unbounded
functions f for which the partial sums of f\circ T^i satisfy both a central
limit theorem and a bounded law of the iterated logarithm. For the same class,
we prove that the partial sums of f(Y_i) satisfy a strong invariance principle.
When the class is larger, so that the partial sums of f\circ T^i may belong to
the domain of normal attraction of a stable law of index p\in (1, 2), we show
that the almost sure rates of convergence in the strong law of large numbers
are the same as in the corresponding i.i.d. case.
