Leviatan , D., O. V. Motorna, and I. A. Shevchuk. 2022. “No Jackson-Type Estimates for Piecewise $q$-Monotone, $q\ge3$, Trigonometric Approximation”. Ukrains’kyi Matematychnyi Zhurnal 74 (5), 662 -75. https://doi.org/10.37863/umzh.v74i5.7081.