@article{IM2_2011_75_3_a1,
     author = {D. I. Borisov},
     title = {On the spectrum of a~two-dimensional periodic operator with a~small localized perturbation},
     journal = {Izvestiya. Mathematics },
     pages = {471--505},
     publisher = {mathdoc},
     volume = {75},
     number = {3},
     year = {2011},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2011_75_3_a1/}
}