@article{MZM_1990_48_1_a20,
     author = {S. R. Gordeev},
     title = {The index of operators with shift, and cyclic subgroups},
     journal = {Matemati\v{c}eskie zametki},
     pages = {146--148},
     publisher = {mathdoc},
     volume = {48},
     number = {1},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1990_48_1_a20/}
}