@article{DE_1989_25_2_a4,
     author = {Yu. V. Malyshev and V. P. Zakharov},
     title = {Investigation of the existence and convexity of limit cycles by the method of generalized {Lyapunov} functions},
     journal = {Differencialʹnye uravneni\^a},
     pages = {212--216},
     publisher = {mathdoc},
     volume = {25},
     number = {2},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1989_25_2_a4/}
}