@article{ITA_1982__16_1_3_0,
     author = {Albert, J.},
     title = {A note on the undecidability of contextfreeness},
     journal = {RAIRO. Informatique th\'eorique},
     pages = {3--11},
     publisher = {EDP-Sciences},
     volume = {16},
     number = {1},
     year = {1982},
     mrnumber = {677652},
     zbl = {0493.68078},
     language = {en},
     url = {http://www.numdam.org/item/ITA_1982__16_1_3_0/}
}