@article{DAN_1966_169_5_a1,
     author = {V. I. Amstislavskii},
     title = {Set-theoretic operations and recursive hierarchies},
     journal = {Doklady Akademii Nauk},
     pages = {995--998},
     publisher = {mathdoc},
     volume = {169},
     number = {5},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1966_169_5_a1/}
}