1. J. Dassow, G. Păun, Regulated rewriting in formal language theory, in: W. Brauer, G. Rozenberg, A. Salomaa (Eds.), EATCS Monographs on Theoretical Computer Science, vol. 18, Springer, Berlin, 1989.
2. J.E. Hopcroft, J.D. Ullman, Introduction to automata theory, languages, and computation, in: M.A. Harrison (Ed.), Addison–Wesley Series in Computer Science, Addison–Wesley, Reading, MA, 1979.
3. An algorithm for the general Petri net reachability problem;Mayr;SIAM J. Comput.,1984
4. More on ET0L systems versus random context grammars;Rozenberg;Inform. Process. Lett.,1976
5. Random context languages;van der Walt;Inform. Process.,1972