2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/89576We give an introduction to an entangled massive system, specifically the neutral kaon system, which has similarities to the entangled two photon system, but, however, also challenging differences.Conference in Commemoration of John S. Bell, Vienna 2000; to be published in Quantum [Un]Speakables, eds. R.A. Bertlmann and A. Zeilinger, Springer Verlag (2001); 20 pagesQuantum PhysicsHigh Energy Physics - Phenomenologytext