2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/72710Using the Spectral Theorem for unbounded self-adjoint operators we prove that any countable family of Lagrangian subspaces of a symplectic Hilbert space admits a common complementary Lagrangian.LaTeX2e, amsart.cls, 4 pages, no figuresFunctional Analysis53D12text