D. Bainov et V. Petrov, NECESSARY AND SUFFICIENT CONDITIONS FOR OSCILLATION OF AUTONOMOUS NEUTRAL DIFFERENTIAL-EQUATIONS WITH DISTRIBUTED DELAY, Journal of mathematical analysis and applications, 182(1), 1994, pp. 202-220
In the paper the autonomous neutral differential equation with distrib
uted delay d/dt[x(t)+delta1.integral/-tau/0 x(t-s) dr1(s)]+delta2.inte
gral-tau/0 x(t-s) dr2(s)=0 is considered,where delta(i)= +/-1, i=1,2.
It is proved that if r1(tau1-) not-equal r1(tau1+), then the necessary
and sufficient condition for all solutions of this equation to oscill
ate is that its corresponding characteristic equation z(1+delta1 integ
ral-tau/0 e(-zs) dr1(s)) +delta2.integral-tau/0 e(-zs) dr2(s) 0 have n
o real roots. (C) 1994 Academic Press, Inc.