Panels (a) and (b): distribution of the abundance ratios [Na/Fe] and [Mg/Fe], as a function of [Fe/H]. Panels (c) and (d): the same ratios, as a function of A(C). The open green triangles and orange circles represent Group II and Group III stars, respectively. The filled green and orange stars are the well-studied CEMP-no stars BD+44 493 and HE 1327-2326, which we take as type examples of Group II and Group III CEMP-no stars, respectively. Note that only stars with available classifications, based on the [Ba/Fe] criterion, are shown. A typical observational error bar is shown in the bottom left of each panel.