R. Kosara, S. Miksch, H. Hauser, J. Schrammel, V. Giller, and M. Tscheligi.
  <b>Useful properties of semantic depth of field for better F+C
  visualization</b>.
  In <i>Proceedings of the Joint Eurographics&mdash;IEEE TCVG Symposium
  on Visualization 2002 (VisSym'02)</i>, pages 205-210, 2002.<br />