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Positive and oscillating solutions of differential equations with delay in critical case. (English) Zbl 0898.34062
The article is devoted to the existence of positive solutions to nonlinear retarded functional-differential equations. Some criteria of existence and some comparison results are proved. The existence of positive and oscillation solutions to the equation x ' (t)=-a(t)x(t-τ) in the critical case is proved.
MSC:
34K11Oscillation theory of functional-differential equations
34C15Nonlinear oscillations, coupled oscillators (ODE)