@article{MT_2001_4_1_a1,
     author = {Yu. L. Ershov},
     title = {Separable {Conservativity}},
     journal = {Matemati\v{c}eskie trudy},
     pages = {18--24},
     publisher = {mathdoc},
     volume = {4},
     number = {1},
     year = {2001},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MT_2001_4_1_a1/}
}