@article{MZM_1991_50_6_a13,
     author = {V. L. Selivanov},
     title = {Jumps of certain classes of $\Delta^0_2$-sets},
     journal = {Matemati\v{c}eskie zametki},
     pages = {122--125},
     publisher = {mathdoc},
     volume = {50},
     number = {6},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1991_50_6_a13/}
}