1. S.A. Avdonin, S.S. Ivanov, Families of Exponentials, Cambridge University, Cambridge, 1995.
2. M. Gugat, Time-parametric control: uniform convergence of the optimal value functions of discretized problems, Control Cybernet. 28(1) (1999) 7.
3. Some trigonometrical inequalities with applications to the theory of series;Ingham;Math. Z.,1936
4. W. Krabs, Time-minimal controllability in the view of optimization, in: A. Auslender, W. Oettli, J. Stoer (Eds.), Optimization and Optimal Control, Springer, Berlin, 1981, p. 211.
5. Optimal control of processes goverend by partial differential equations part ii: Vibrations;Krabs;Z. Oper. Res.,1982