[Ba/Eu] versus [Fe/H] observed in Ursa Minor dSph galaxy compared to the predictions of the chemical evolution model for Ursa Minor. The solid line represents the best model (ν= 0.2 Gyr−1, wi = 10) and the dotted lines the lower (ν= 0.05 Gyr−1) and upper (ν= 0.5 Gyr−1) limits for the SF efficiency. The thin line represents the best model without Ba production in massive stars.