@techreport {TR-1980-007,
   type = {Technical Report},
   author = {Barry Levine },
   title = {The Use of Tree Derivatives and a Sample Support Parameter for Inferring Tree Systems},
   institution = {University of Oregon, Computer and Information Sciences Department},
   number = TR-1980-007,
   year = 1980,
   note = {Available at \url{https://www.cs.uoregon.edu/Reports/TR-1980-007.pdf}},
}