1. L. S. Pontryagin, V. G. Boltyanskii, R. V. Gamkrelidze, and E. F. Mishchenko, The Mathematical Theory of Optimal Processes (Fizmatgiz, Moscow, 1961; Pergamon, Oxford, 1964); 4th ed. (Nauka, Moscow, 1983).
2. F. P. Vasil’ev, Optimization Methods (MTsNMO, Moscow, 2011), Parts 1, 2 [in Russian].
3. A. S. Antipin, L. A. Artem’eva, and F. P. Vasil’ev, “Extragradient method for solving an optimal control problem with implicitly specified boundary conditions,” Comput. Math. Math. Phys. 57 (1), 64–70 (2017) [transl. from Zh. Vychisl. Mat. Mat. Fiz. 57 (1), 49–54 (2017)].
4. A. N. Tikhonov and V. Ya. Arsenin, Solutions of Ill-Posed Problems (Nauka, Moscow, 1974; J. Wiley & Sons, New York, 1977); 3rd ed. (Nauka, Moscow, 1986).
5. A. Bakushinsky and A. Goncharsky, Iterative Methods for Solving Ill-Posed Problems (Nauka, Moscow, 1989). Partial Engl. transl.: Ill-Posed Problems: Theory and Applications (Kluwer, Dordrecht, 1994), Math. Appl. 301.