@article{DAN_1985_285_4_a3,
     author = {Yu. L. Ershov},
     title = {$\Sigma$-definability in admissible sets},
     journal = {Doklady Akademii Nauk},
     pages = {792--795},
     publisher = {mathdoc},
     volume = {285},
     number = {4},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1985_285_4_a3/}
}