@article{SM_1974_23_3_a3,
     author = {L. D. Pustyl'nikov},
     title = {Stable and oscillating motions in nonautonomous dynamical systems. {A~generalization} of {C.} {L.~Siegel's} theorem to the nonautonomous case},
     journal = {Sbornik. Mathematics},
     pages = {382--404},
     year = {1974},
     volume = {23},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1974_23_3_a3/}
}