@article{CMUC_1973_14_3_a9,
     author = {Mezn{\'\i}k, Ivan},
     title = {On some closure properties of generable languages},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {541--552},
     year = {1973},
     volume = {14},
     number = {3},
     mrnumber = {0337062},
     zbl = {0284.68061},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1973_14_3_a9/}
}