@article{MZM_2002_72_5_a4,
     author = {Kh. K. Ishkin},
     title = {A {Criterion} for {Spectrum} {Decomposition}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {670--681},
     year = {2002},
     volume = {72},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2002_72_5_a4/}
}