Left: the oxygen abundance versus the logarithm of the gas fraction from observed galaxies compared with the prediction of the closed-box model (solid black line) together with the 1σ limits (dashed black line). Middle: the logarithm of the gas fraction versus the stellar mass. Right: the ratio of the SFR(NUV) to the mass of Hi versus the stellar mass. In all three plots, Hi normal and Hi deficient galaxies are plotted as solid blue and open red circles, respectively.