@article{DAN_1972_204_3_a19,
     author = {S. Ts. Akopyan and V. N. Zharkov and V. M. Lyubimov},
     title = {The perturbation theory for {Earth} torsional oscillation. {Second} approximation},
     journal = {Doklady Akademii Nauk},
     pages = {596--599},
     publisher = {mathdoc},
     volume = {204},
     number = {3},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_204_3_a19/}
}