@techreport{Jones&Gibbons93:Linear,
  title = "Linear-time Breadth-first Tree Algorithms: An Exercise in the Arithmetic of Folds and Zips",
  author = "Geraint Jones and Jeremy Gibbons",
  year = "1993",
  institution = "Dept of Computer Science, University of Auckland",
  month = "may",
  note = "Also IFIP Working Group 2.1 working paper 705~WIN-2",
  number = "No.\,71",
  url = "http://www.cs.ox.ac.uk/people/jeremy.gibbons/publications/linear.ps.gz",
}