@article{KYB_1970__6_2_a3,
     author = {Navr\'atil, Emil},
     title = {Context-free grammars with regular conditions},
     journal = {Kybernetika},
     pages = {--126},
     publisher = {mathdoc},
     volume = {06},
     number = {2},
     year = {1970},
     mrnumber = {0278861},
     zbl = {0208.02002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/KYB_1970__6_2_a3/}
}