1. R. J. R. Back. On the Correctness of Refinement Steps in Program Development. PhD thesis, Department of Computer Science, University of Helsinki, Helsinki, 1978. Report A-1978-4.
2. R. J. R. Back. Correctness Preserving Program Refinements: Proof Theory and Applications, volume 131 of Mathematical Center Tracts. Mathematical Centre, Amsterdam, 1980.
3. R. J. R. Back. On correct refinement of programs. J. Computer and Systems Sciences, 23(1):49–68, August 1981.
4. R. J. R. Back. Procedural abstraction in the refinement calculus. Reports on computer science and mathematics 55, Åbo Akademi, 1987.
5. R. J. R. Back. A calculus of refinements for program derivations. Acta Informatica, 25:593–624, 1988.