Babenko, V. F., and G. S. Zhiganova. “On the Best L2 -Approximations of Functions by Using Wavelets”. Ukrains’kyi Matematychnyi Zhurnal 60, no. 8 (August 25, 2008): 1119 – 1127. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3229.