1. On the structure of polynomially bounded D0L systems;Ehrenfeucht;Fund. Inform.,1979
2. On ambiguity in E0L systems;Ehrenfeucht;Theoret. Comput. Sci.,1980
3. Introduction to Formal Language Theory;Harrison,1978
4. Synchronized E0L forms;Maurer;Theoret. Comput. Sci.,1980