1. Ten years of Hoare's logic, a survey—Part I;Apt;ACM TOPLAS,1981
2. Correctness Preserving Program Refinements: Proof Theory and Applications;Back,1980
3. Mathematical Theory of Program Correctness;de Bakker,1980
4. Correctness of programs with function procedures;de Bakker,1982
5. A formalized proof system for total correctness of while programs;Bergstra,1981