@Article{SCI:Sch2009a,
  author =    "M. Schott and V. Pegoraro and C.D. Hansen and K.
              Boulanger and K. Bouatouch",
  title =     "A Directional Occlusion Shading Model for
              Interactive Direct Volume Rendering",
  journal =   "Computer Graphics Forum",
  volume =    "28",
  number =    "3",
  pages =     "855--862",
  year =      "2009",
  publisher = "Wiley-Blackwell",
  month =     "jun",
  doi =       "10.1111/j.1467-8659.2009.01464.x",
  url =       "http://www.sci.utah.edu/publications/Sch2009a/EuroVis09DirectionalOcclusionShading.pdf",
}