2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/183328Some experimental studies of $η$ production and $η$ interactions performed or presently under way by the GEM collaboration at COSY Jülich are reviewed.invited talk, ETA'05 Workshop, 15.- 17. Sept. 2005, Cracow, PolandNuclear Experimenttext