@article{MZM_1999_65_4_a14,
     author = {O. N. Ageev},
     title = {On the spectral multiplicity function for dynamical systems},
     journal = {Matemati\v{c}eskie zametki},
     pages = {619--622},
     year = {1999},
     volume = {65},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1999_65_4_a14/}
}