1. Some questions of phrase structure grammars;ÁbrahÁm;Computational Linguistics,1965
2. An analog of a theorem about context-free languages;Brainerd;Information and Control,1968
3. Simple matrix languages;Ibarra;Information and Control,1970
4. An hierarchy between context-free and context-sensitive languages;Kasai;J. Comput. System Sci.,1970
5. Programmed grammars and classes of formal languages;Rosenkrantz;J. Assoc. Comput. Mach.,1969