1. The decidability of the equivalence of context-free grammar forms;Blattner,1979
2. Context-free grammar forms;Cremers;J. Comput. System Sci.,1975
3. The structure of context-free grammatical families;Cremers;J. Comput. System Sci.,1977
4. Algebraic and Automata-Theoretic Properties of Formal Languages;Ginsburg,1975
5. A survey of grammar forms — 1977;Ginsburg;Acta Cybernet.,1978