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Existence of periodic solution for first order nonlinear neutral delay equations. (English) Zbl 1009.34073
The authors discuss the following nonlinear neutral delay equation $[x(t)+cx(t-\tau)]'+g(t, x(t-\sigma))=p(t),$ with $$\tau\geq 0, \sigma\geq 0$$ and $$|c|<1$$. By using the coincidence degree theory, they derive sufficient conditions for the existence of a periodic solution to the above equation.

##### MSC:
 34K40 Neutral functional-differential equations 34K13 Periodic solutions to functional-differential equations 34C25 Periodic solutions to ordinary differential equations
##### Keywords:
nonlinear; neutral delay equation; periodic solution
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