2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/223879Baiocchi et al. generalized a few years ago a classical theorem of Ingham and Beurling by means of divided differences. The optimality of their assumption has been proven by the third author of this note. The purpose of this note to extend these results to vector coefficient sums.5 pagesClassical Analysis and ODEs42B99; 42A99text