Rudolf Freund, Gheorghe Paun. On the Number of Non-terminal Symbols in Graph-Controlled, Programmed and Matrix Grammars. In Maurice Margenstern, Yurii Rogozhin, editors, Machines, Computations, and Universality, Third International Conference, MCU 2001, Chisinau, Moldavia, May 23-27, 2001, Proceedings. Volume 2055 of Lecture Notes in Computer Science, pages 214-225, Springer, 2001. [doi]
Abstract is missing.