MASSERA-TYPE THEOREM TO A CLASS OF SEMI-LINEAR DIFFERENTIAL EQUATIONS
Abstract
In the present work, by applying a Massera-type theorem, we derive sufficient conditions for the existence and uniqueness of periodic solutions to a class of partial functional differential equations of the form

here the operator A(t): E ⊇ D(A) → E is τ-periodic and possibly unbounded; the operator Γ(·, x(·)) takes values in a Banach space E, the function α takes values in the Banach space D(A), and are τ-periodic.
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