@article{MT_1996_30_a5,
     author = {O. V. Kudinov},
     title = {Compressed systems of finite approximations for sets in the class $\Sigma_2^0$},
     journal = {Matemati\v{c}eskie trudy},
     pages = {111--113},
     publisher = {mathdoc},
     volume = {30},
     year = {1996},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MT_1996_30_a5/}
}