@article{ZNSL_1991_190_a7,
     author = {S. V. Khryashchev},
     title = {On the discrete spectrum of a perturbed periodic {Schr\"odinger} operator},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {157--162},
     publisher = {mathdoc},
     volume = {190},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1991_190_a7/}
}