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2. J.-L. Lions, Contróle optimal de systémes gouvernés par des équations aux dérivées partielles, (Dunod, Paris, 1968; Mir, Moscow, 1972).
3. V. G. Litvinov, Optimization in Elliptic Boundary Value Problems with Applications to Mechanics (Nauka, Moscow, 1987) [in Russian].
4. K. A. Lur’e, Optimal Control in Problems of Mathematical Physics (Nauka, Moscow, 1975) [in Russian].
5. U. E. Raitum, Optimal Control in Problems for Elliptic Equations (Zinatne, Riga, 1989) [in Russian].