@conference{gibbons06essence,
  author = "Jeremy Gibbons and Bruno C. d. S. Oliveira",
  booktitle = "Workshop on Mathematically Structured Functional Programming (MSFP 2006)",
  editor = "Conor McBride and Tarmo Uustalu",
  location = "Kuressaare, Estonia",
  month = "July",
  title = "The Essence of The Iterator Pattern",
  url = "http://www.comlab.ox.ac.uk/jeremy.gibbons/publications/iterator.pdf",
  year = "2006",
}