1. R. V. Gamkrelidze, Foundations of Optimal Control [in Russian], Tbilisi Univ. (1977).
2. J. Warga, Optimal Control of Differential and Functional Equations, Academic Press, New York (1972).
3. L. S. Pontryagin, V. G. Boltyanskii, R. V. Gamkrelidze, and E. F. Mishchenko, The Mathematical Theory of Optimal Processes, Wiley, New York (1962).
4. A. Ya. Dubovitskii and A. A. Milyutin, ?Extremal problems in the presence of constraints,? Zh. Vychisl. Mat. Mat. Fiz.,5, No. 3, 395?453 (1965).
5. A. Ya. Dubovitskii and A. V. Dubovitskii, ?Necessary conditions for a strong minimum in optimal control problems with the degeneration of the end and phase constraints,? Usp. Mat. Nauk,40, No. 2, 175?176 (1985).