@article{DE_1971_7_6_a0,
     author = {K. G. Val\={e}\={e}v and M. Ya. Vazhgovskaya},
     title = {An investigation of the stability of the solutions of a system of second order linear differential equations with periodic coefficients},
     journal = {Differencialʹnye uravneni\^a},
     pages = {955--960},
     publisher = {mathdoc},
     volume = {7},
     number = {6},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1971_7_6_a0/}
}