@techreport {TR-1977-002,
   type = {Technical Report},
   author = {Arthur Farley, Stephen Hedetniemi, Sandra Mitchell, Andrzej Proskurowski},
   title = {Minimal Broadcast Graphs},
   institution = {University of Oregon, Computer and Information Sciences Department},
   number = TR-1977-002,
   year = 1977,
   note = {Available at \url{https://www.cs.uoregon.edu/Reports/TR-1977-002.pdf}},
}