@article{KYB_1966_2_6_a1,
     author = {Gruska, Jozef},
     title = {On sets generated by context-free grammars},
     journal = {Kybernetika},
     pages = {483--493},
     year = {1966},
     volume = {2},
     number = {6},
     mrnumber = {0209091},
     zbl = {0158.25308},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/KYB_1966_2_6_a1/}
}