N and O abundances in metal-poor halo stars from Spite et al. (2005). A typical error bar is indicated top left; the bulge star 10 464 is shown as a green star symbol. Solid (open) symbols indicate unmixed (mixed) stars and the dashed line illustrates the mean value of the unmixed sample. The red line is the best-fit relation for the mixed stars, determined by Spite et al. (2005), extrapolated toward our bulge star (dotted line).