1. On formal properties of simple phrase structure grammars;Bar-Hillel,1960
2. On certain formal properties of grammars;Chomsky;Inform. Control,1959
3. Formal properties of grammars;Chomsky,1963
4. Finite state languages;Chomsky;Inform. Control,1958
5. The linguistic approach to pattern analysis: literature survey;Feder,1966