1. Two-symbol complete E0L forms;Culik;Theoret. Comput. Sci,1978
2. Context-free grammar forms with strict interpretations;Maurer;J. Comput. System Sci,1980
3. A super normal form theorem for context-free grammars;Maurer,1980
4. Synchronized E0L forms;Maurer;Theoret. Comput. Sci,1980
5. Dense hierarchies of grammatical families;Maurer;J. Assoc. Comput. Mach,1981