@article{DAN_1981_258_4_a9,
     author = {M. A. Brutyan and S. V. Lyapunov},
     title = {On the second variation of the {Riabouschinsky} functional},
     journal = {Doklady Akademii Nauk},
     pages = {812--814},
     publisher = {mathdoc},
     volume = {258},
     number = {4},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1981_258_4_a9/}
}