Am. Zhao et Jr. Yan, EXISTENCE OF POSITIVE SOLUTIONS FOR DELAY-DIFFERENTIAL EQUATIONS WITHIMPULSES, Journal of mathematical analysis and applications, 210(2), 1997, pp. 667-678
A powerful comparison result and some effective sufficient conditions
for existence of positive solutions of the delay differential equation
with impulses [GRAPHICS] are obtained by establishing the equivalence
of existence of positive solutions of() and solutions of an integral
equation. (C) 1997 Academic Press.