@article{VUU_2005_1_a10,
     author = {N. I. Pletnikova},
     title = {On levels of the {Schr\"edinger} operator with a perturbed step potential},
     journal = {Vestnik Udmurtskogo universiteta. Matematika, mehanika, kompʹ\^uternye nauki},
     pages = {155--166},
     year = {2005},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VUU_2005_1_a10/}
}