Yessenbayeva, G., Yesbayev, A., Syzdykova, N., & Smirnova, M. (2023). On the function approximation by trigonometric polynomials and the properties of families of function classes over harmonic intervals. Bulletin of the Karaganda University. Mathematics Series, 111(3), 181–190. https://doi.org/10.31489/2023m3/181-190