2 citations to https://www.mathnet.ru/eng/dan22306

1. N. V. Balashevich, R. Gabasov, F. M. Kirillova, “Numerical methods for open-loop and closed-loop optimization of linear control systems”, Comput. Math. Math. Phys., 40:6 (2000), 799–819      
2. V. G. Boltyanskii, “The method of tents in the theory of extremal problems”, Russian Math. Surveys, 30:3 (1975), 1–54