A(Li) versus [Fe/H] when selecting thick disk stars using kinematical or chemical criteria. Panel a: uses the kinematical criteria as defined in Bensby et al. (2003) and selects stars that are at least 10 times more likely to be thick disk stars (T D/D > 10); panel b: stars that are at least two times more likely to be thick disk stars (T D/D > 2). Panels c–h: uses α-enhancement as a criterion to select thick disk stars. Panel d: A(Li) trends when using [Si/Fe] as a proxy for α-enhancement, requiring stars to have [Si/Fe] values above the solid red line in the [Si/Fe]-[Fe/H] plot shown in panel c. Panel e: we illustrate the effect of uncertainties in the abundance ratios by lowering the limit to the dashed red line in panel c. The α-enhancement criterion but using [Mg/Fe] instead is shown in panels f –h. Upper limit Li abundances were not included in the plots.