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@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/} }
Yu. L. Ershov. $\Sigma$-definability in admissible sets. Doklady Akademii Nauk, Tome 285 (1985) no. 4, pp. 792-795. http://geodesic.mathdoc.fr/item/DAN_1985_285_4_a3/