Equidistribution speed for endomorphisms of projective spaces

Let f be a non-invertible holomorphic endomorphism of P(k), f(n) its iterate of order n and mu the equilibrium measure of f. We estimate the speed of convergence in the following known result. If a is a Zariski generic point in P(k), the probability measures, equidistributed on the preimages of a under f(n), converge to mu as n goes to infinity.