Abundances in unevolved stars: the ratios [Mg/Fe], [Si/Fe] and [Ca/Fe] for the program stars (red open circles) compared to those measured (grey and blue squares) by our group in other extremely metal-poor dwarf stars (Bonifacio et al. 2009, 2012; Bonifacio et al. 2018; Caffau et al. 2013a,b). Blue (resp. grey) squares represent the stars which have been observed with UVES (resp. X-shooter). Pink squares represent dwarf stars analysed by Matsuno et al. (2017). Black dashed lines represent the linear fit to our data. Typical errors are represented in the lower left par of each panel.