@MastersThesis{SCI:Cal2005d,
  author =    "S.P. Callahan",
  title =     "The k-Buffer and its Applications to Volume
              Rendering",
  year =      "2005",
  school =    "School of Computing, University of Utah",
  note =      "Masters Thesis",
  keywords =  "volume rendering",
  url =       "http://www.sci.utah.edu/publications/stevec05/thesis.pdf",
}