Characterisation of substructure A and the independent clusters #12, #38, #28, and #40. Left: distribution in the L_⊥ − L_z plane. The original sample of halo stars is shown as a grey background. Middle: normalised MDFs for the three largest (in number of stars) structures/clusters. As an inset we add the MDF of cluster #12 alone to highlight its apparently double population. See text for details. Right: normalised MDFs for clusters #28 and #40, showing a narrow MDF. We add the MDF of substructure A (dashed, blue line) for comparison. Error bars in all plots are computed assuming Poisson statistics.