1. Comparative schematology;Paterson,1970
2. Program schemes, recursion schemes and formal languages;Garland;J. Comp. Syst. Sci.,1973
3. On classes of program schemata;Constable;SIAM J. Computing,1972
4. Flowchart schemata with counters;Plaisted,1972
5. Program schemas with equality;Chandra,1972