@article{MZM_1993_53_5_a2,
     author = {B. N. Biyarov and M. Otelbaev},
     title = {A description of normal extensions},
     journal = {Matemati\v{c}eskie zametki},
     pages = {21--28},
     publisher = {mathdoc},
     volume = {53},
     number = {5},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1993_53_5_a2/}
}