@article{KYB_1972_8_3_a2,
     author = {Gruska, Jozef},
     title = {On the size of context-free grammars},
     journal = {Kybernetika},
     pages = {213--218},
     year = {1972},
     volume = {8},
     number = {3},
     mrnumber = {0331877},
     zbl = {0241.68037},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/KYB_1972_8_3_a2/}
}