We show that the Lusin area integral or the square function on the unit ball
of \C^n, regarded as an operator in weighted space L2(w) has a linear
bound in terms of the invariant A2 characteristic of the weight. We show a
dimension-free estimate for the ``area-integral'' associated to the weighted
L2(w) norm of the square function. We prove the equivalence of the classical
and the invariant A2 classes.Comment: 11 pages, to appear in Arkiv for Matemati