@article{DE_1992_28_10_a9,
     author = {Ch. A. Skhalyaho},
     title = {The oscillatory nature of solutions of systems of two differential equations with sign-variable right-hand sides},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1736--1747},
     publisher = {mathdoc},
     volume = {28},
     number = {10},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1992_28_10_a9/}
}