@article{DE_1991_27_2_a20,
     author = {I. E. Vitrichenko},
     title = {On the stability in a critical case of a zero and a pair of pure imaginary roots of an $n$-th order nonautonomous nonlinear equation},
     journal = {Differencialʹnye uravneni\^a},
     pages = {350--354},
     publisher = {mathdoc},
     volume = {27},
     number = {2},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1991_27_2_a20/}
}