THE STABILITY OF NEUTRAL DIFFERENTIAL SYSTEMS WITH VARIABLE DELAY

It is known that determination of the stability of neutral differential systems is a difficult and complicated problem, on which little material has been published so far. In [1]—[4], the stability of neutral differential systems had been investigated, with the general result that the delay Δ（t） needs to satisfy 0<Δ0≤Δ（t）≤Δ.

A SIMPLE ALGEBRAIC CRITERION FOR ALL THE ZEROS OF THE FUNCTION Det(a_(ij)+b_(ij)e^(-λτ)-δ_(ij)λ)(?)f_n(λ,τ) DISTRIB-UTED IN THE LEFT OF COMPLEX PLANE

Lemma. If there exists a group of nonnegatiue and differential functions V_k(t): R_o→R+ (k=1, 2, …, n) such