@article{DE_1992_28_3_a4,
     author = {Yu. A. Mitropol'skii and V. L. Kulik},
     title = {Invariant manifolds of autonomous differential equations, and sign-variable {Lyapunov} functions},
     journal = {Differencialʹnye uravneni\^a},
     pages = {398--405},
     publisher = {mathdoc},
     volume = {28},
     number = {3},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1992_28_3_a4/}
}