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), pp. 736–750. doi:10.37863/umzh.v72i6.1107.