@article{RM_1971_26_4_a16,
     author = {L. D. Pustyl'nikov},
     title = {A~generalization of two theorems of {C.} {L.~Siegel} to the nonautonomous case},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     year = {1971},
     volume = {26},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1971_26_4_a16/}
}