Babenko VF, Parfinovych NV. On the best $L_1$-approximations of functional classes by splines under restrictions imposed on their derivatives. Ukr. Mat. Zhurn. [Internet]. 1999Apr.25 [cited 2024Jul.27];51(4):435-44. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/4629