@techreport {TR-1991-020,
   type = {Technical Report},
   author = {Claude Saunders, Art Farley},
   title = {Reasoning About Spatial Structure in Landscapes with Geographic Information Systems},
   institution = {University of Oregon, Computer and Information Sciences Department},
   number = TR-1991-020,
   month = 9,
   year = 1991,
   note = {Available at \url{https://www.cs.uoregon.edu/Reports/TR-1991-020.pdf}},
}