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@article{PORMA_1954__13_3_114738, author = {Halfar, Edwin}, title = {The isolated points of a set}, journal = {Portugaliae mathematica}, pages = {125--128}, publisher = {mathdoc}, volume = {13}, number = {3}, year = {1954}, mrnumber = {0072457}, zbl = {0057.38703}, language = {en}, url = {http://geodesic.mathdoc.fr/item/PORMA_1954__13_3_114738/} }
Halfar, Edwin. The isolated points of a set. Portugaliae mathematica, Tome 13 (1954) no. 3, pp. 125-128. http://geodesic.mathdoc.fr/item/PORMA_1954__13_3_114738/