@article{10_21136_CMJ_1964_100629,
     author = {Fabian, V\'aclav},
     title = {Structural unambiguity of formal languages},
     journal = {Czechoslovak Mathematical Journal},
     pages = {394--430},
     publisher = {mathdoc},
     volume = {14},
     number = {3},
     year = {1964},
     doi = {10.21136/CMJ.1964.100629},
     mrnumber = {0171639},
     zbl = {0278.68062},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CMJ.1964.100629/}
}