Sulphur abundances derived in this work. The symbols are the same as in Fig. 1. The starting points of the horizontal (vertical) arrows indicate the upper limit of the metallicity (sulphur abundance). The (upper limit of) sulphur abundance for these stars is derived with respect to the literature (IQM) metallicity. The solid line shows the enrichment assumed for the other α-elements. The dotted lines cross at the solar values, which correspond to log ϵ(Fe)_⊙ = 7.45 and log ϵ(S)_⊙ = 7.14 (Grevesse et al. 2007).