@techreport {TR-1981-002,
   type = {Technical Report},
   author = {Arthur Farley, Andrzej Proskurowski},
   title = {Computing the Line Index of Balance of Signed Outerplanar Graphs},
   institution = {University of Oregon, Computer and Information Sciences Department},
   number = TR-1981-002,
   year = 1981,
   note = {Available at \url{https://www.cs.uoregon.edu/Reports/TR-1981-002.pdf}},
}