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@article{DAN_1976_228_2_a0, author = {V. G. Boltyanskii}, title = {Generalization of a theorem of {B.~Sz.-Nagy}}, journal = {Doklady Akademii Nauk}, pages = {265--268}, publisher = {mathdoc}, volume = {228}, number = {2}, year = {1976}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1976_228_2_a0/} }
V. G. Boltyanskii. Generalization of a theorem of B.~Sz.-Nagy. Doklady Akademii Nauk, Tome 228 (1976) no. 2, pp. 265-268. http://geodesic.mathdoc.fr/item/DAN_1976_228_2_a0/