a) Dendogram plot of the hierarchical tree resulting from the cluster analysis of the 14-species chemical abundances of the sample without errors. The x-axis gives the HD numbers of the stars and the y-axis represents the Euclidean distance, in the normalized abundance space, between subgroups. The two main groups are identified by the labeled boxes. b) Scandium abundances as a function of strontium. The two main groups identified above are projected with different symbol: filled triangle stand for CP stars, open circles represent normal stars.