@article{DAN_1972_203_6_a4,
     author = {V. A. Iliushkin},
     title = {On complexity of the grammatical description of contextually free languages},
     journal = {Doklady Akademii Nauk},
     pages = {1244--1245},
     publisher = {mathdoc},
     volume = {203},
     number = {6},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_203_6_a4/}
}