@article{DAN_1969_185_6_a15,
     author = {P. E. Krasnushkin},
     title = {Normal wave expansion in a spherically stratified medium},
     journal = {Doklady Akademii Nauk},
     pages = {1262--1265},
     publisher = {mathdoc},
     volume = {185},
     number = {6},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_185_6_a15/}
}