Stability for impulsive delay differential equations

In this paper, the stability for the scalar impulsive delay differential equation y'(t) + a(t)y(t) + F(t, y (.)) = 0, t >= 0, t not equal tau(k), y(tau(+)(k)) - y(tau(k)) = I-k(y(tau(k))), k = 1, 2,..., k ->infinity lim tau(k) = infinity, where delay arguments may be bounded or unbounded is investigated. Some new stability theorems are established which improve and extend several known results in the literature. (c) 2005 Elsevier Ltd. All rights reserved.