Solodov А. “a Asymptotic Behavior of the Sum of Sines Series in the Zero Neighborh”. Bulletin of L.N. Gumilyov Eurasian National University. Mathematics, Computer Science, Mechanics Series, vol. 125, no. 4, Dec. 2018, pp. 108-12, https://bulmathmc.enu.kz/index.php/main/article/view/30.