@article{DAN_1971_196_6_a2,
     author = {A. G. Dragalin and V. A. Lyubetskii and V. I. Fukson},
     title = {Definable sequences of countable ordinals},
     journal = {Doklady Akademii Nauk},
     pages = {1263--1265},
     publisher = {mathdoc},
     volume = {196},
     number = {6},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_196_6_a2/}
}