1. Assigning meanings to programs;Floyd,1967
2. An axiomatic basis for computer programming;Hoare;Commun. ACM,1969
3. Guarded commands, nondeterminacy and formal derivation of programs;Dijkstra;Commun. ACM,1975
4. On the correctness of refinement in program development;Back,1978
5. Correctness Preserving Program Refinements: Proof Theory and Applications;Back,1980