2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/82020A review is first presented of the Hall--Post inequalities relating $N$-body to $(N-1)$-body energies of quantum bound states. These inequalities are then applied to delimit, in the space of coupling constants, the domain of Borromean binding where a composite system is bound while smaller subsystems are unbound.5 pages, Dedicated to V.B. Belyaev for his 70th birthday, to be included in a jubilee volume, edited by A.K.Motovilov and F.M.Pen'kovNuclear TheoryQuantum Physicstext