@article{DAN_1964_159_4_a0,
     author = {M. Ya. Azbel'},
     title = {On the spectrum of difference equations with periodic coefficients},
     journal = {Doklady Akademii Nauk},
     pages = {703--706},
     publisher = {mathdoc},
     volume = {159},
     number = {4},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_159_4_a0/}
}