Mp. Chen et al., THE PERSISTENCE OF NONOSCILLATORY SOLUTIONS OF DELAY-DIFFERENTIAL EQUATIONS UNDER IMPULSIVE PERTURBATIONS, Computers & mathematics with applications, 27(8), 1994, pp. 1-6
We obtain a sufficient condition for the persistence of nonoscillatory
solutions of the delay differential equation x'(t) + p(t)x(t - tau) =
0, under impulsive perturbations.