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1. 1. 1987.
Necessary and sufficient condition for oscillations of neutral differential equations
Abstract Consider the neutral delay differential equation where p ∈ R, τ ≥ 0, q1 > 0, σ1 ≥ 0, for i = 1, 2, …, k. We prove the following result. Theorem. A necessary and sufficient condition for the oscillation of all solutions of Eq. (1) is that the characteristic equation has no real roots.