@techreport {TR-1981-003,
   type = {Technical Report},
   author = {Maciej Syslo, Andrzej Proskurowski},
   title = {On Halin Graphs+},
   institution = {University of Oregon, Computer and Information Sciences Department},
   number = TR-1981-003,
   year = 1981,
   note = {Available at \url{https://www.cs.uoregon.edu/Reports/TR-1981-003.pdf}},
}