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By means of an abstract continuation theorem, the existence criteria are established for the positive periodic solutions of a neutral functional differential equation d N d t=N(t)[a(t)-β(t)N(t)-b(t)N(t-σ(t))-c(t)N′(t-τ(t))].
By means of an abstract continuation theorem, the existence criteria are established for the positive periodic solutions of a neutral functional differential equation contribution d N dt = N (t) [a (t) -β (t) N (t) -b (t) N (t-σ (t)) - c (t) N ’(t-τ (t))]