1. G. A. Bliss, Lectures On the Calculus of Variations (University of Chicago Press, Chicago, 1946; Inostrannaya Literatura, Moscow, 1950).
2. A. A. Fel’dbaum, Foundations of the Theory of Optimal Automatic Systems (Fizmatgiz, Moscow, 1963) [in Russian].
3. A. E. Bryson and Ho Yu-Chi, Applied Optimal Control: Optimization, Estimation, and Control (Hemisphere, Washington, 1969; Mir, Moscow, 1972).
4. A. M. Letov, “Analytical Design of Controllers, I,” Avtom. Telemekh. 21, 661–665 (1960).
5. R. E. Kalman, “On the General Theory of Control Systems,” in Proc. of the First IFAC Congress on Automatic Control, Moscow, 1961 (Akad. Nauk SSSR, Moscow, 1961), Vol. 1, pp. 521–547.