@inproceedings{ExecutablePredicates,
  title = "Programs as executable predicates",
  author = "A. W. Roscoe and C.A.R. Hoare",
  year = "1984",
  booktitle = "{Proceedings of FGCS84 (ICOT, editors)}",
  pages = "220--228",
  url = "http://www.cs.ox.ac.uk/people/bill.roscoe/publications/5.pdf",
}