Kolomoitsev, Yu. S. 2007. “On Moduli of Smoothness and Fourier Multipliers in $L_p, 0 < <i>p</I> &lt; 1$”. Ukrains’kyi Matematychnyi Zhurnal 59 (9), 1221–1238. https://umj.imath.kiev.ua/index.php/umj/article/view/3383.