@article{MZM_1967_2_6_a5,
     author = {V. N. Polyakov},
     title = {A certain class of formally normal operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {605--614},
     year = {1967},
     volume = {2},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1967_2_6_a5/}
}