Necessary Conditions for the Existence of a Saddle Point in one Optimal Control Problem for Systems of Hyperbolic Equations. Eur. J. Pure Appl. Math. [Internet]. 2021 Nov. 10 [cited 2024 Nov. 24];14(4):1402-14. Available from: https://www.ejpam.com/index.php/ejpam/article/view/4135