Ignat'ev, A. O. “On Equiasymptotic Stability of Solutions of Doubly-Periodic Impulsive Systems”.
Ukrains’kyi Matematychnyi Zhurnal
, vol. 60, no. 10, Oct. 2008, pp. 1317–1325,
https://umj.imath.kiev.ua/index.php/umj/article/view/3246
.