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@article{PORMA_1962__21_3_114888, author = {Morgado, Jos\'e}, title = {A characterization of the closure operators by means of one axiom}, journal = {Portugaliae mathematica}, pages = {155--156}, publisher = {mathdoc}, volume = {21}, number = {3}, year = {1962}, mrnumber = {0148573}, zbl = {0107.25203}, language = {en}, url = {http://geodesic.mathdoc.fr/item/PORMA_1962__21_3_114888/} }
Morgado, José. A characterization of the closure operators by means of one axiom. Portugaliae mathematica, Tome 21 (1962) no. 3, pp. 155-156. http://geodesic.mathdoc.fr/item/PORMA_1962__21_3_114888/