Almost periodic solutions of second-order neutral delay-differential equations with piecewise constant arguments (Q1883449)

The author proves a theorem on the existence of almost-periodic solutions for a class of second-order neutral delay differential equations with piecewise constant arguments of the form \[ \frac{d^2}{dt^2}(x(t)+x(t-1))=qx([t])+f(t), \] in which \([\bullet]\) denotes the greatest integer function, \(q\) is a nonzero constant, and \(f(t)\) is almost-periodic.