1. Context-free grammar forms;Cremers;J. Comput. System Sci.,1975
2. The Mathematical Theory of Context-Free Languages;Ginsburg,1966
3. Characteristic and ultrarealtime languages;Greibach;Inform. Contr.,1971
4. Control sets on context-free grammar forms;Greibach;J. Comput. System Sci.,1977
5. Two Extensions of KASAI's Universal Context-Free Grammar;Hart,1976