Comparison of our results with those from Önehag et al. (2014), Gao et al. (2018), and Souto et al. (2018) for the average elemental abundances for subgiant and turn-off stars. Top panel: comparison of the average elemental abundances for the subgiant stars. Bottom panel: comparison of the average elemental abundances for the turn-off stars (black, green, blue, and red symbols represent the results from this work, Önehag et al. 2014, Gao et al. 2018, and Souto et al. 2018, respectively).