A state-dependent delay equation with chaotic solutions

We exhibit a scalar-valued state-dependent delay differential equation $$x′(t)=f(x(t−d(xt)))$$ that has a chaotic solution. This equation has continuous (semi-strictly) monotonic negative feedback, and the quantity $t−d(xt)$ is strictly increasing along solutions.

Electronic Journal of the Qualitative Theory of Differential Equations, 22(1-20)