1. P. America and J.J.M.M. Rutten. Solving Reflexive Domain Equations in a Category of Complete Metric Spaces. Journal of Computer and System Sciences, 39(3):343–375, 1989.
2. R.-J.R. Back. Correctness Preserving Program Refinements: Proof Theory and Applications, volume 131 of Mathematical Centre Tracts. CWI, Amsterdam, 1980.
3. E. Best. Towards Compositional Predicate Transformer Semantics for Concurrent Programs. In J.W. de Bakker, 25 jaar Semantiek, pages 111–117, CWI, Amsterdam, 1989.
4. M.M. Bonsangue and J.N. Kok. Relating Multifunctions and Predicate Transformers through Closure Operators. pages 822–843. LNCS 789, 1994.
5. M.M. Bonsangue, J.N. Kok, and E.P. de Vink. Metric Predicate Transformers: Towards a Notion of Refinement for Concurrent Programs. Report IR-371, Vrije Universiteit Amsterdam, 1994. Available through anonymous ftp from ftp.cs.vu.nl as pub/papers/theory/IR-371.ps.Z.