The authors study the existence of almost periodic solutions for the following partial neutral functional-differential equations
where is a linear operator on a Banach space , not necessarily densely defined and satisfies the known Hille-Yosida condition; is endowed with the uniform topology; is a bounded linear operator having the form . By using the variation of constants formula and the spectral decomposition of the phase space developed in M. Adimy et al. [Can. Appl. Math. Q. 9, No. 1, 1–34 (2001; Zbl 1112.34341)], they prove that the existence of an almost periodic solution is equivalent to the existence of a bounded solution on .