DZYUBENKO, G. A. Stechkin-type estimate for nearly copositive approximation of periodic functions. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 72, n. 5, p. 628–634, 2020. DOI: 10.37863/umzh.v72i5.1127. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1127. Acesso em: 8 dec. 2025.