1. Tree generating regular systems;Brainerd;Inf. and Control,1969
2. Some formal properties of a class of nondeterministic program schemata;Ito;9th Symp. Switching and Aut. theory,1968
3. Regular expressions and the equivalence of programs;Kaplan;J. Comp. Syst. Sci.,1969
4. On infinite modes;Koster;ALGOL Bulletin,1969
5. On the formal description of PL/1;Lucas;Ann. Rev. Autom. Progr.,1963