1. K. Abrahamson, correspondence.
2. An introduction to Algorithmic Logic;Banachowski,1977
3. Finite models of deterministic propositional dynamic logic;Ben-Ari,1981
4. Equations between regular terms and an application to Process Logic;Chandra,1981
5. Propositional dynamic logic of regular programs;Fischer;J. Comput. System Sci.,1979