2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/78114Every frame in Hilbert space contains a subsequence equivalent to an orthogonal basis. If a frame is n-dimensional then this subsequence has length (1 - ε) n. On the other hand, there is a frame which does not contain bases with brackets.16 pages, LaTeXFunctional Analysis46C05; 46B07text