@article{ITA_1984__18_1_23_0,
     author = {Pin, Jean-Eric},
     title = {Hi\'erarchies de concat\'enation},
     journal = {RAIRO. Informatique th\'eorique},
     pages = {23--46},
     publisher = {EDP-Sciences},
     volume = {18},
     number = {1},
     year = {1984},
     mrnumber = {750449},
     zbl = {0559.68062},
     language = {fr},
     url = {http://www.numdam.org/item/ITA_1984__18_1_23_0/}
}