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@article{DAN_1957_115_5_a3, author = {I. I. Parovichenko}, title = {Certain special classes of topological spaces and $\delta s$-operations}, journal = {Doklady Akademii Nauk}, pages = {866--868}, publisher = {mathdoc}, volume = {115}, number = {5}, year = {1957}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1957_115_5_a3/} }
I. I. Parovichenko. Certain special classes of topological spaces and $\delta s$-operations. Doklady Akademii Nauk, Tome 115 (1957) no. 5, pp. 866-868. http://geodesic.mathdoc.fr/item/DAN_1957_115_5_a3/