@article{SM_1988_59_2_a16,
     author = {A. G. Eliseev and S. A. Lomov},
     title = {The theory of singular perturbations in the case of spectral singularities of a~limit operator},
     journal = {Sbornik. Mathematics},
     pages = {541--555},
     publisher = {mathdoc},
     volume = {59},
     number = {2},
     year = {1988},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1988_59_2_a16/}
}