Babenko VF, Gorbenko ME. On the uniqueness of an element of the best $L_1$-approximation for functions with values in a banach space. Ukr. Mat. Zhurn. [Internet]. 2000Jan.25 [cited 2024Sep.1];52(1):30-4. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/4393