@article{AUPO_2004_43_1_a5,
     author = {Chajda, Ivan},
     title = {Class preserving mappings of equivalence systems},
     journal = {Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica},
     pages = {61--64},
     year = {2004},
     volume = {43},
     number = {1},
     mrnumber = {2124603},
     zbl = {1077.08001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AUPO_2004_43_1_a5/}
}