@article{CMJ_2003_53_1_a16,
     author = {Hala\v{s}, Radom{\'\i}r and Hort, Daniel},
     title = {A characterization of 1-, 2-, 3-, 4-homomorphisms of ordered sets},
     journal = {Czechoslovak Mathematical Journal},
     pages = {213--221},
     year = {2003},
     volume = {53},
     number = {1},
     mrnumber = {1962010},
     zbl = {1015.06002},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMJ_2003_53_1_a16/}
}