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@article{PORMA_1964__23_1_114915, author = {Hammer, Preston C.}, title = {Extended topology: perfect sets}, journal = {Portugaliae mathematica}, pages = {27--34}, publisher = {mathdoc}, volume = {23}, number = {1}, year = {1964}, mrnumber = {0203663}, zbl = {0151.29301}, language = {en}, url = {http://geodesic.mathdoc.fr/item/PORMA_1964__23_1_114915/} }
Hammer, Preston C. Extended topology: perfect sets. Portugaliae mathematica, Tome 23 (1964) no. 1, pp. 27-34. http://geodesic.mathdoc.fr/item/PORMA_1964__23_1_114915/