1. R. J. Back and J. von Wright. Refinement Calculus: A Systematic Introduction. Springer-Verlag, 1998.
2. Lect Notes Comput Sci;S. Bensalem,1996
3. M. J. Butler, J. Grundy, T. Långbacka, R. Rukšenas, and J. von Wright. The Refinement Calculator: Proof Support for Program Refinement. In Proc. FMP’97-Formal Methods Pacific, Discrete Mathematics and Theoretical Computer Science, Wellington, New Zealand, July 1997. Springer-Verlag.
4. Lect Notes Comput Sci;L. A. Dennis,2000
5. E. W. Dijkstra. A Discipline of Programming. Prentice-Hall International, 1976.