1. Refinement calculus I: Sequential nondeterministic programs;Back,1990
2. A Discipline of Programming;Dijkstra,1976
3. Data refinement of maps;Gardiner,1990
4. An algebraic construction of predicate transformers;Gardiner,1992
5. Data refinement of predicate transformers;Gardiner;Theoret. Comput. Sci.,1991