Examples of the methodology to estimate RV shifts between the spectra. Left-hand panels: VFTS 003 is a relatively bright narrow-lined supergiant. The upper panel shows the Si iii 4553 Å line in the template spectrum (MJD = 54 804.148, black line) and at MJD = 55 108.309 (red). The lower panel shows the original (black line) and smoothed (red) cross-correlation function in velocity space; no significant velocity shifts were found for this target. Right-hand panels: VFTS 189 is a relatively faint, broad-lined, main-sequence star. The upper panel shows the He i 4388 Å line in the template spectrum (MJD = 54 867.160, black) and at MJD = 54 824.242 (red). The lower panel shows the original and smoothed cross-correlation functions in velocity space; the estimated RV shift between these was ~200 km s^-1.