@article{NANO_2019_10_5_a1,
     author = {T. H. Rasulov and N. A. Tosheva},
     title = {Analytic description of the essential spectrum of a family of $3\times 3$ operator matrices},
     journal = {Nanosistemy: fizika, himi\^a, matematika},
     pages = {511--519},
     publisher = {mathdoc},
     volume = {10},
     number = {5},
     year = {2019},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/NANO_2019_10_5_a1/}
}