@Article{SCI:Att2006a,
  author =    "L. Atty and N. Holzschuch and M. Lapierre and
              J.-M. Hasenfratz and C.D. Hansen and F.X.
              Sillion",
  title =     "Soft Shadow Maps: Efficient Sampling of Light
              Source Visibility",
  journal =   "Computer Graphics Forum",
  volume =    "25",
  number =    "4",
  pages =     "725--741",
  year =      "2006",
  url =       "http://www.sci.utah.edu/publications/atty06/Soft_Shadow_Maps.pdf",
}