@TechReport{SCI:Par94b,
  author =    "S.G. Parker and C.R. Johnson",
  title =     "Interactive Manipulation of Contour Data Using the
              Layers Program - User Guide",
  number =    "UUCS-94-014",
  year =      "1994",
  institution = "University of Utah",
  type =      "School of Computing Technical Report",
  keywords =  ", pse, problem solving environments",
  url =       "http://www.sci.utah.edu/publications/sparker94/layers.ps",
}