Gunko, M.S., Babenko, V.F. and Parfinovych, N.V. 2020. Optimal recovery of elements from Hilbert space and their scalar products by Fourier coefficients known with error. Ukrains’kyi Matematychnyi Zhurnal. 72, 6 (Jun. 2020), 736-750. DOI:https://doi.org/10.37863/umzh.v72i6.1107.