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2. The existence of an optimal Lyapunov function and of a continuous optimal controller for one problem in the analytical design of controllers;Al'brekht;Differential'nye Uravneniya,1965
3. Suboptimal design of intentionally nonlinear controllers;Rekasius;IEEE Trans. Aut. Control,1964
4. Uber die Sub-Optimale Regelung von Nichtlinearen Systemen;Rekasius;Regelundstechnik,1964
5. An approach to sub-optimal feedback control of nonlinear system;Garrard;Int. J. Control,1967