@techreport {TR-1980-009,
   type = {Technical Report},
   author = {Patrick Shen-pei Wang},
   title = {A Syntactic Representation of Two-Dimensional Patterns},
   institution = {University of Oregon, Computer and Information Sciences Department},
   number = TR-1980-009,
   year = 1980,
   note = {Available at \url{https://www.cs.uoregon.edu/Reports/TR-1980-009.pdf}},
}