@article{ITA_1979__13_2_189_0,
     author = {Greibach, S. A.},
     title = {One counter languages and the chevron operation},
     journal = {RAIRO. Informatique th\'eorique},
     pages = {189--194},
     publisher = {EDP-Sciences},
     volume = {13},
     number = {2},
     year = {1979},
     mrnumber = {543940},
     zbl = {0441.68081},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1979__13_2_189_0/}
}