8 pages and 6 figures (macro asp2006.sty included). An invited
  contribution to the intl. conference "From Stars to Galaxies: Building the
  pieces to build up the Universe" (Venezia, Italy, 16-20/Oct/2006). ASP Conf.
  Series, eds. A. Vallenari, R. Tantalo, L. Portinari and A. Moretti. Further
  info at author's web site (see http://www.bo.astro.it/~eps/home.html)