@article{MMO_1963_12_a0,
     author = {V. K. Mel'nikov},
     title = {On the stability of a center for time-periodic perturbations},
     journal = {Trudy Moskovskogo matemati\v{c}eskogo ob\^{s}estva},
     pages = {3--52},
     publisher = {mathdoc},
     volume = {12},
     year = {1963},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MMO_1963_12_a0/}
}