@article{DAN_1964_158_3_a5,
     author = {I. P. Natanson},
     title = {Saturation classes in the theory of singular integrals},
     journal = {Doklady Akademii Nauk},
     pages = {520--523},
     year = {1964},
     volume = {158},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_158_3_a5/}
}