Mathematical Experimentation in Time-Lag Modulation
Equations of the form du/dt = g(u(t),u(h(t)))
arise in a number of scientific contexts.  The 
authors point out some interesting properties of the
solution u'(t) = -u(t-1-k*sin(wt))+sin(at).  These 
properties were obtained by means of numerical solution.
CACM October, 1966
Bellman, R.
Buell, J.
Kalaba, R.
