@article{CMUC_1991_32_2_a0,
     author = {Poljak, Svatopluk},
     title = {Coloring digraphs by iterated antichains},
     journal = {Commentationes Mathematicae Universitatis Carolinae},
     pages = {209--212},
     year = {1991},
     volume = {32},
     number = {2},
     mrnumber = {1137780},
     zbl = {0758.05053},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMUC_1991_32_2_a0/}
}