@article{SM_1981_40_2_a4,
     author = {A. N. Degtev},
     title = {On reducibilities of numerations},
     journal = {Sbornik. Mathematics},
     pages = {193--204},
     publisher = {mathdoc},
     volume = {40},
     number = {2},
     year = {1981},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1981_40_2_a4/}
}