@article{MZM_1992_51_4_a13,
     author = {M. A. Pankratov},
     title = {Evolution of the complex spectrum of a periodic operator},
     journal = {Matemati\v{c}eskie zametki},
     pages = {101--108},
     publisher = {mathdoc},
     volume = {51},
     number = {4},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1992_51_4_a13/}
}