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Oscillations of solutions of neutral differential equations with positive and negative coefficients. (English) Zbl 1005.34056
The authors consider the neutral differential equation with positive and negative coefficients of the form $\frac{d}{dt}[y(t)-R(t)y(t-r)]+P(t)y(t-\tau)-Q(t)y(t-\sigma)=0,$ where $$r\in (0, \infty)$$, and $$\tau , \sigma \in \mathbb{R}^+$$ with $$\tau \geq\sigma$$; $$P, Q, R\in C([t_0, \infty), \mathbb{R}^+), P(t)-Q(t-\tau+\sigma)\geq 0$$ and not identically zero. Several new sufficient conditions for the oscillation of all solutions to the above equation are obtained without the following usual hypothesis: $$\int_{t_0}^{\infty}[P(s)-Q(s-\tau+\sigma)] ds=\infty$$.

##### MSC:
 34K11 Oscillation theory of functional-differential equations 34K40 Neutral functional-differential equations
##### Keywords:
neutral differential equations; oscillation
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##### References:
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