1. The correctness of programs;Manna;J. Computer Systems Sciences,1969
2. Formalization of properties of functional programs;Manna;J. ACM,1970
3. A heuristic program for solving problems stated as nondeterministic procedures;Fikes,1968
4. Nondeterministic algorithms;Floyd;J. ACM,1967
5. Termination of algorithms;Manna;Ph.D. Thesis, Carnegie-Mellon University,1968