1. I. V. Girsanov, Lectures on the Mathematical Theory of Extremum Problems (Springer, New York, 1972).
2. Yu. G. Evtushenko, Methods for Solving Extremal Problems and their Application in Optimization Systems (Nauka, Moscow, 1982) [in Russian].
3. A. I. Egorov, Optimal Control of Thermal and Diffusion Processes (Nauka, Moscow, 1978) [in Russian].
4. R. P. Fedorenko, Approximate Solution of Optimal Control Problems (Nauka, Moscow, 1978) [in Russian].
5. J. L. Lions, Optimal Control of Systems Governed by Partial Differential Equations (Springer, New York, 1971).