@article{IVP_2018_26_6_a7,
     author = {V. V. Uchaikin and V. A. Litvinov},
     title = {Nonlinear perturbation theory based on the variational principle: {Model} examples},
     journal = {Izvestiya VUZ. Applied Nonlinear Dynamics},
     pages = {82--98},
     publisher = {mathdoc},
     volume = {26},
     number = {6},
     year = {2018},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVP_2018_26_6_a7/}
}