@article{ITA_1991__25_5_473_0,
     author = {Geffert, Viliam},
     title = {Normal forms for phrase-structure grammars},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {473--496},
     publisher = {EDP-Sciences},
     volume = {25},
     number = {5},
     year = {1991},
     mrnumber = {1144010},
     zbl = {0755.68092},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1991__25_5_473_0/}
}