@article{ARM_1977__13_3_a2,
     author = {Chvalina, Jan},
     title = {Isomorphic algebraic pre-closures and equivalent set-systems},
     journal = {Archivum mathematicum},
     pages = {141--147},
     publisher = {mathdoc},
     volume = {13},
     number = {3},
     year = {1977},
     mrnumber = {0463076},
     zbl = {0373.08001},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ARM_1977__13_3_a2/}
}