1. Structural equivalence of extended context-free and E0L grammars;Cameron,1995
2. Bracketed context-free languages;Ginsburg;J. Comput. System Sci.,1967
3. The strong structural equivalence of ET0L grammars;Istrate,1994
4. Complexity of some problems concerning L systems;Jones;Math. Systems Theory,1979
5. Parenthesis grammars;McNaughton;J. ACM,1967