Top panel: comparison between the RV measured on LAMOST spectra (Table A.1) with literature values based mainly on high-resolution spectra (open circles). Filled circles refer to stars with multiple LAMOST observations. The continuous line is the one-to-one relationship. The differences, shown in the bottom panel, show a mean value of ≃+5 km s^-1 (dashed line) and a standard deviation of about 14 km s^-1 (dotted lines). Discrepant values are indicated with filled circles enclosed in squares in both panels.