@article{DAN_1988_301_3_a8,
     author = {A. P. Makhmudov and Z. S. Aliyev},
     title = {Nondifferentiable perturbations of spectral problems for a pair of},
     journal = {Doklady Akademii Nauk},
     pages = {551--554},
     publisher = {mathdoc},
     volume = {301},
     number = {3},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1988_301_3_a8/}
}