2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/116220The contribution of strange sea quarks to the proton mass and spin, as well as the related pion-nucleon sigma term, are briefly revisited, in the light of new experimental and lattice results. Also the predictions of chiral perturbation theory for these quantities are discussed.5 pages, plain LaTeXHigh Energy Physics - Phenomenologytext