@techreport {TR-1997-005,
   type = {Technical Report},
   author = {Zena Ariola, Stefan Blom},
   title = {Lambda Calculi plus Letrec},
   institution = {University of Oregon, Computer and Information Sciences Department},
   number = TR-1997-005,
   month = 7,
   year = 1997,
   note = {Available at \url{https://www.cs.uoregon.edu/Reports/TR-1997-005.pdf}},
}