@article{IM2_2020_84_6_a2,
     author = {S. A. Nazarov},
     title = {Threshold resonances and virtual levels in the spectrum of~cylindrical and periodic waveguides},
     journal = {Izvestiya. Mathematics },
     pages = {1105--1160},
     publisher = {mathdoc},
     volume = {84},
     number = {6},
     year = {2020},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_2020_84_6_a2/}
}