@article{DAN_1957_115_3_a17,
     author = {B. I. Stepanov and P. A. Apanasevich},
     title = {Natural profile of energy levels},
     journal = {Doklady Akademii Nauk},
     pages = {488--490},
     publisher = {mathdoc},
     volume = {115},
     number = {3},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_115_3_a17/}
}