@article{DE_1991_27_5_a6,
     author = {Yu. V. Malyshev and V. P. Zakharov},
     title = {Linear generalized {Lyapunov} functions and limit cycles},
     journal = {Differencialʹnye uravneni\^a},
     pages = {777--781},
     publisher = {mathdoc},
     volume = {27},
     number = {5},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1991_27_5_a6/}
}