2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/208520Recently a new proof was given for Beurling's Ingham type theorem on one-dimensional nonharmonic Fourier series, providing explicit constants. We improve this result by applying a short elementary method instead of the previous complex analytical approach. Our proof equally works in the multidimensional case.8 pagesClassical Analysis and ODEs42B99; 42A99text