1. Angell T. S. and Kirsch A., On the necessary conditions for optimal control of retarded systems, Applied Mathematics and Optimization, 22, (1990), 117–145.
2.Banks H. T., Necessary condition for control problems with variable time lags, SIAM Journal on Control, 8 (1), (1968), 9–47.
3.Banks H. T. and Burns J. A., Hereditary control problem: Numerical methods based on averaging approximations, SIAM Journal on Control and Optimization, 16 (2), (1978), 169–208.
4. Betts J. T, Campbell S. L. and Thompson K. C., Solving optimal control problems with control delays using direct transcription, Applied Numerical Mathematics, 108, (2016), 185-203.
5. Friesz T. L., Dynamic Optimization and Differential Games, Springer: New York, 2010.
6. Gollmann L, Kern D. and Maurer H., Optimal control problems with delays in state and control variables subject to mixed control-state constraints, Optim. Control Appl. Meth, 30 (4), (2009), 341–365.
7.Gollmann L. and Maurer H., Theory and applications of optimal control problems with multiple time-delays, Journal of Industrial & Management Optimization, 10 (2), (2014), 413-441.
8. Halanay A., Optimal controls for systems with time lag, SIAM Journal on Control, 6, (1968), 215–234.
9.Hoseini S. M. and Marzban H. R., Costate Computation by an Adaptive Pseudospectral Method for Solving Optimal control problems with piecewise constant Time Lag, Journal of Optim Theory Appl, 170 (3), (2016), 735–755.
10. Jajarmi A. and Hajipour M., An efficient finite difference method for the time-delay optimal control problems with time-varying delay, Asian Journal of Control, 19 (2), (2017), 554–563.
11. Jajarmi A., Hajipour M. and Baleanu D., A new approach for the optimal control of time-varying delay systems with external persistent matched disturbances, Journal of Vibration and Control, 24 (19), (2018), 4505–4512.
12.Kharatishvili GL, Maximum Principle in the theory of Optimal time-delay Processes,, Doklady Akademii Nauk, USSR, 136 (1), (1961), 39-42.
13. Liu C., Loxton R., Teo K. L. and Wang S., Optimal state-delay control in nonlinear dynamic systems, Automatica, 135, (2022), 109981.
14. Liu C., Gong Z., Teo K. L. and Wang S., Optimal control of nonlinear fractional-order systems with multiple time-varying delays, Journal of Optimization Theory and Applications, 193 (1), (2022), 856-876.
15.Mirhosseini-Alizamini S. M., Effati S. and Heydari A., An iterative method for suboptimal control of linear time-delayed systems, Systems and Control Letters, 82, (2015), 40–50.
16.Marzban H. R. and Hoseini S. M., Optimal control of linear multi-delay systems with piecewise constant delays, IMA Journal of Mathematical Control and Information, 00, (2016), 1–30.
17.Marzban H. R., Pirmoradian H., A direct approach for the solution of nonlinear optimal control problems with multiple delays subject to mixed state-control constraints, Applied Mathematical Modelling, 53, (2018), 189-213.
18.Rakhshan S. A. and Effati S., Fractional optimal control problems with time- varying delay: A new delay fractinal Euler-Lagrange equations, Science Direct Journal of the Franklin Institute, 357 (10), (2020): 5954-5988.
19.Soliman M. A. and Ray W. H., On the optimal control of systems having pure time delay and singular arcs, International Journal of Control, 16 (5),(1972): . 963-976
20.Wu D. and Bai Y., Time- scaling transformation for optimal control problem with time- varying delay, Discrete and continuous dynamical systems series s, 13 (6), (2020), 1683–1695.