@InProceedings{DasSti_j2007_b, author = {J{\"u}rgen~Dassow and Raflf~Stiebe}, title = {Nonterminal Complexity of Some Operations on Context-Free Languages}, booktitle = {{9th International Workshop on Descriptional Complexity of Formal Systems, DCFS 2007, Nov\'y Smokovec, Slovakia, July 20--23, 2007, Proceedings}}, year = 2007, editor = {Viliam~Geffert and Giovanni~Pighizzini}, publisher = {University Ko\v{s}ice, Slovakia}, pages = {162--169} }