@article{IM2_2018_82_6_a3,
     author = {S. A. Nazarov},
     title = {Breakdown of cycles and the possibility of opening spectral gaps
},
     journal = {Izvestiya. Mathematics },
     pages = {1148--1195},
     publisher = {mathdoc},
     volume = {82},
     number = {6},
     year = {2018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2018_82_6_a3/}
}