@unpublished{Dijkstra82:From,
  title = "{EWD821}: From Predicate Transformers to Predicates",
  author = "Edsger W. Dijkstra",
  year = "1982",
  month = "April 20",
  note = "Original, handwritten, ``Dedicated by the Tuesday Afternoon Club to C. A. R. Hoare at the occasion of his being elected Fellow of the Royal Society''",
}