V. F. Babenko and G. S. Zhiganova, “On the best L2 -approximations of functions by using wavelets”, Ukr. Mat. Zhurn., vol. 60, no. 8, pp. 1119 – 1127, Aug. 2008, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3229