DzyubenkoG. A. “Stechkin-Type Estimate for Nearly Copositive Approximation of Periodic Functions”. Ukrains’kyi Matematychnyi Zhurnal 72, no. 5 (April 29, 2020): 628–634. Accessed December 4, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1127.