@incollection{BirddeMoor93:Relational,
  title = "Relational Program Derivation and Context-Free Language Recognition",
  author = "Richard Bird and Oege de Moor",
  year = "1994",
  booktitle = "A Classical Mind: Essays in Honour of {C}.~{A}.~{R}.~{H}oare",
  chapter = "2",
  editor = "A. W. Roscoe",
  publisher = "Prentice-Hall",
}