1. M. Blattner and S. Ginsburg, Position-restricted grammar forms, Theoret. Comput. Sci., in press.
2. Context-free grammar forms;Cremers;J. Comput. System Sci.,1975
3. S. Ginsburg, personal communication.
4. On strict interpretations of grammar forms;Ginsburg;Math. Systems Theory,1979
5. E0L forms;Maurer;Acta Dorm.,1977