@article{ITA_1976__10_2_33_0,
     author = {Brzozowski, Janusz A.},
     title = {Hierarchies of aperiodic languages},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {33--49},
     publisher = {Dunod-Gauthier-Villars},
     address = {Paris},
     volume = {10},
     number = {R2},
     year = {1976},
     mrnumber = {428813},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ITA_1976__10_2_33_0/}
}