1. K. Balachandran (1990), Time optimal control of nonlinear systems,Advances in Modelling and Simulation 18 (4), 47?54.
2. W. G. Boltjanski (1972), The separation properties of a systems of convex cones (Russian),Izvestija Akad. Nauk Armen. SSR 7 (4), 250?257.
3. W. G. Boltjanski (1976),Optimale Steuerung diskreter Systems, Akademische Verlagsgesellschaft Gest & Portig K.-G., Leipzig.
4. L. Cesari (1983),Optimization ? Theory and Applications. Problems with Ordinary Differential Equations, Springer-Verlag, New York, Heidelberg, Berlin.
5. M. Goebel (1989), On control problems for a quasilinear second order ordinary differential equation,Math. Nachr. 142, 277?286.