@article{ND_2012_8_3_a7,
     author = {Vladimir Yu. Ol'shanskii},
     title = {On quadratic integral {Poincare--Zhukovsky's} equations},
     journal = {Russian journal of nonlinear dynamics},
     pages = {523--540},
     publisher = {mathdoc},
     volume = {8},
     number = {3},
     year = {2012},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ND_2012_8_3_a7/}
}