Voir la notice de l'article provenant de la source Math-Net.Ru
@article{MZM_1967_1_2_a1, author = {S. B. Stechkin}, title = {Best approximation of linear operators}, journal = {Matemati\v{c}eskie zametki}, pages = {137--148}, publisher = {mathdoc}, volume = {1}, number = {2}, year = {1967}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1967_1_2_a1/} }
S. B. Stechkin. Best approximation of linear operators. Matematičeskie zametki, Tome 1 (1967) no. 2, pp. 137-148. http://geodesic.mathdoc.fr/item/MZM_1967_1_2_a1/