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@article{DAN_1975_222_2_a5, author = {I. I. Parovichenko}, title = {On the commutativity of $\delta s$-operations}, journal = {Doklady Akademii Nauk}, pages = {284--287}, publisher = {mathdoc}, volume = {222}, number = {2}, year = {1975}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1975_222_2_a5/} }
I. I. Parovichenko. On the commutativity of $\delta s$-operations. Doklady Akademii Nauk, Tome 222 (1975) no. 2, pp. 284-287. http://geodesic.mathdoc.fr/item/DAN_1975_222_2_a5/