@TechReport{SCI:Kni2003c,
  author =    "J.M. Kniss and S. Premoze and M. Ikits and A.E.
              Lefohn and C.D. Hansen",
  title =     "Closed Form Solution to the Volume Rendering
              Integral with Gaussian Transfer Functions",
  number =    "UUCS-03-013",
  year =      "2003",
  institution = "University of Utah School of Computing",
  type =      "Technical Report",
  keywords =  "scalar field methods, volume rendering, transfer
              functions, Level-set methods, level-set methods",
  url =       "http://www.sci.utah.edu/publications/jmk03/UUCS-03-013.pdf",
}