1. Ten years of Hoare's logic—A survey;Apt,1979
2. Correctness Preserving Program Refinements: Proof Theory and Applications;Back,1980
3. Recursive Procedures;De Bakker,1973
4. Mathematical Theory of Program Correctness;De Bakker,1980
5. Floyd's principle, correctness theories and program equivalence;Bergstra;Theoret. Comput. Sci.,1982