@inproceedings{Das_j2003_b, author = {J{\"u}rgen~Dassow}, title = {On the Differentiation Function of some Language Generating Devices}, editor = {Masami~Ito and Teruo~Imaoka}, booktitle = {Words, Languages and Combinatorics {III} -- Proceedings of the Third International Conference, Kyoto, Japan, March 14--18, 2000}, publisher = worldsci, pages = {151--161}, year = 2003, isbn = {981-02-4948-9} }