@article{CMJ_2009__59_1_a2,
     author = {Skowronek-Kazi\'ow, J.},
     title = {Properties of digraphs connected with some congruence relations},
     journal = {Czechoslovak Mathematical Journal},
     pages = {39--49},
     publisher = {mathdoc},
     volume = {59},
     number = {1},
     year = {2009},
     mrnumber = {2486614},
     zbl = {1221.05183},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CMJ_2009__59_1_a2/}
}