@incollection{BirdMeertens87:Two,
  title = "Two Exercises Found In a Book on Algorithmics",
  author = "Richard S. Bird and Lambert Meertens",
  year = "1987",
  booktitle = "Program Specification and Transformation",
  editor = "Lambert Meertens",
  pages = "451--457",
  publisher = "North-Holland",
}