@article{DAN_1961_138_4_a5,
     author = {S. G. Krein and E. M. Semenov},
     title = {A scale of spaces},
     journal = {Doklady Akademii Nauk},
     pages = {763--766},
     publisher = {mathdoc},
     volume = {138},
     number = {4},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_138_4_a5/}
}