Author comment for 2003A&A...404..819L:
Three typos affect the Appendix. The paper content and results are unaffected.
Appendix A. Below Eq. (A7), 2F1(a,b,c,0)=1 instead of
2F1(a,b,c,0)=0. In Eq. (A8) Rt^3 should appear instead of Rt^4.
Appendix B. In Eq. (B2) a factor v_i is missing inside the integral.
Author comment submitted on 26 July, 2004 by Luca Ciotti (luca.ciotti@unibo.it)