@article{IVM_1973_5_a9,
     author = {V. N. Polyakov},
     title = {A~multiplication theorem for the characteristic functions of linear operators},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {73--76},
     publisher = {mathdoc},
     number = {5},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1973_5_a9/}
}