@article{MZM_1997_61_1_a4,
     author = {Yu. N. Bibikov},
     title = {Conservation and bifurcation of an invariant torus of a~vector field},
     journal = {Matemati\v{c}eskie zametki},
     pages = {34--44},
     publisher = {mathdoc},
     volume = {61},
     number = {1},
     year = {1997},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1997_61_1_a4/}
}