@article{ELMA_1972__27_141081,
     author = {Hans-Joachim Vollrath},
     title = {Zur {Charakterisierung} von {Kongruenzrelationen} durch {Abbildungen.}},
     journal = {Elemente der Mathematik},
     pages = {133--134},
     publisher = {mathdoc},
     volume = {27},
     year = {1972},
     zbl = {0438.08001},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1972__27_141081/}
}