@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/}
}