Deceptively cold dust in the massive starburst galaxy GN20 at z~4 nork Cortzen, I, Magdis, GE, Valentino, F, Daddi, E, Liu, D, Rigopoulou, D, Sargent, M, Riechers, D, Cormier, D, Hodge, JA, Walter, F, Elbaz, D, Béthermin, M, Greve, TR, Kokorev, V, Toft, S