@article{01204397,
title = {Second method of Lyapunov and existence of periodic solutions of linear impulsive differential-difference equations.},
journal = {Divulgaciones Matem\'aticas},
volume = {5},
year = {1997},
pages = {29-37},
zbl = {0907.34009},
language = {en},
url = {http://dml.mathdoc.fr/item/01204397}
}
Bainov, D.D.; Stamova, I.M. Second method of Lyapunov and existence of periodic solutions of linear impulsive differential-difference equations.. Divulgaciones Matemáticas, Tome 5 (1997) pp. 29-37. http://gdmltest.u-ga.fr/item/01204397/