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@article{DAN_1961_137_4_a16, author = {B. M. Stepanov}, title = {A formal definition of $R$-operations}, journal = {Doklady Akademii Nauk}, pages = {818--821}, publisher = {mathdoc}, volume = {137}, number = {4}, year = {1961}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1961_137_4_a16/} }
B. M. Stepanov. A formal definition of $R$-operations. Doklady Akademii Nauk, Tome 137 (1961) no. 4, pp. 818-821. http://geodesic.mathdoc.fr/item/DAN_1961_137_4_a16/