Romanyuk, V. S. “Multiple Haar Basis and M-Term Appriximations for Functions from the Besov Classes. I”. Ukrains’kyi Matematychnyi Zhurnal 68, no. 4 (April 25, 2016): 551–562. Accessed December 5, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/1860.