@article{JCEM_2017_4_3_a2,
     author = {E. V. Kirillov and G. A. Zakirova},
     title = {A direct spectral problem for $L$-spectrum of the perturbed operator with a multiple spectrum},
     journal = {Journal of computational and engineering mathematics},
     pages = {19--26},
     publisher = {mathdoc},
     volume = {4},
     number = {3},
     year = {2017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JCEM_2017_4_3_a2/}
}