Anti-correlations between light elements: Na-O (upper panel) and Mg-Al (lower panel). GIRAFFE stars are indicated by red filled circles and UVES stars by filled blue squares; upper limits in O are shown as arrows. The error bars are the cluster average internal (star-to-star) errors for each element for the GIRAFFE sample in red and UVES in blue (see text). In the upper panel we indicate the separation between P and I, and I and E populations, according to Carretta et al. (2009a).