@article{AA_1996_8_1_a0,
     author = {M. Sh. Birman},
     title = {The discrete spectrum of the periodic {Schr\"odinger} operator perturbed by a decreasing potential},
     journal = {Algebra i analiz},
     pages = {3--20},
     publisher = {mathdoc},
     volume = {8},
     number = {1},
     year = {1996},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AA_1996_8_1_a0/}
}