Difference between the [α/Fe] values for Mg, Ca, Ti and Si obtained in this work and the values presented in AB10 calculated as Δ[α/Fe] = [α/Fe]_this work − [α/Fe]_AB10. The dashed line indicates the mean value of the difference and the dotted lines show the 1σ range for each element. In particular, disk giants used by AB10 to calculate their internal zero points are shown as red filled stars.