1. I. Gumowski and C. Mira,Optimization in Control Theory and Practice. Cambridge University Press, Cambridge (1968).
2. R. Datko, J. Lagness and M.P. Poilis, An example on the effect of time delays in boundary feedback stabilization of wave equations.SIAM J. Control Optim.24(1986) 152–156.
3. R. Datko, Not all feedback stabilized hyperbolic systems are robust with respect to small time delay in their feedbacks.SIAM J. Control Optim.26(1988) 697–713.
4. Use of time-delay actions in the controller design
5. Performance improvement using time delays in multivariable controller design