@article{ND_2007_3_1_a3,
     author = {B. S. Bardin},
     title = {On nonlinear oscillations of {Hamiltonian} system in case of fourth order resonance},
     journal = {Russian journal of nonlinear dynamics},
     pages = {57--74},
     publisher = {mathdoc},
     volume = {3},
     number = {1},
     year = {2007},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ND_2007_3_1_a3/}
}