@article{ITA_2004__38_3_257_0,
     author = {Dassow, J\"urgen and Mitrana, Victor and P\u{a}un, Gheorghe and Stiebe, Ralf},
     title = {On differentiation functions, structure functions, and related languages of context-free grammars},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {257--267},
     publisher = {EDP-Sciences},
     volume = {38},
     number = {3},
     year = {2004},
     doi = {10.1051/ita:2004013},
     mrnumber = {2076403},
     zbl = {1082.68049},
     language = {en},
     url = {http://www.numdam.org/articles/10.1051/ita:2004013/}
}