@Article{SCI:Lju2016a,
  author =    "P. Ljung and J. Kr{\"u}ger and E. Gr{\"o}ller and M.
              Hadwiger and C. D. Hansen and and A. Ynnerman",
  title =     "State of the Art in Transfer Functions for Direct
              Volume Rendering",
  journal =   "Computer Graphics Forum",
  volume =    "35",
  number =    "3",
  pages =     "669--691",
  year =      "2016",
  publisher = "Wiley-Blackwell",
  month =     "June",
  doi =       "10.1111/cgf.12934",
  url =       "http://www.sci.utah.edu/publications/Lju2016a/Transfer-Function-Design-2016.pdf",
}