1. Tree Generating Systems and Tree Automata;Brainerd,1967
2. The Minimalization of Tree Automata;Brainerd;Inform. Control,1968
3. Regular Canonical Systems;BÜchi;Archiv. fÜr Mathematische Logik und Grundlagenforschung,1964
4. On Certain Formal Properties of Grammars;Chomsky;Inform. Control,1959
5. Computability and Unsolvability;Davis,1958