@article{DAN_1980_254_6_a26,
     author = {S. P. Alliluev and V. M. Vainberg and V. L. Eletskii and V. S. Popov},
     title = {Logarithmic perturbation theory for excited levels},
     journal = {Doklady Akademii Nauk},
     pages = {1392--1396},
     publisher = {mathdoc},
     volume = {254},
     number = {6},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1980_254_6_a26/}
}