@inproceedings{Gibbons&Oliveira2006:Essence,
  title = "The Essence of the Iterator Pattern",
  author = "Jeremy Gibbons and Bruno C\'esar dos Santos Oliveira",
  year = "2006",
  booktitle = "Mathematically-Structured Functional Programming",
  editor = "Conor McBride and Tarmo Uustalu",
  note = "Superseded by \cite{Gibbons&Oliveira2008:Essence}",
  url = "http://www.comlab.ox.ac.uk/jeremy.gibbons/publications/iterator-msfp.pdf",
}