Pyragas, Kestutis Max Planck Institute for the Physics of Complex Systems, Max Planck Society;
https://journals.aps.org/pre/abstract/10.1103/PhysRevE.66.026207 (Publisher version)
Pyragas, K. (2002). Analytical properties and optimization of time-delayed feedback control. Physical Review E, 66(2): 026207. doi:10.1103/PhysRevE.66.026207.