Three example spectra with S/N ≈ 50 from different clusters covering the whole range of metallicities in our sample. The observed spectra are shown in black, overplotted with the best fitting Voigt profiles. The areas marked in yellow were used for the continuum correction, while those in blue define the line bandpasses that were used for fitting the Voigt profiles and calculating the equivalent widths. The given metallicities are mean cluster metallicities from Dias et al. (2016).