Rest-frame velocity histograms of the “literature sample” clusters with a public redshift set. In addition to the same details presented in Appendix A, we also report here the public value of (and its uncertainty) for each cluster as listed in Table 1, and we show them with red Gaussian curves. Although our analysis sometimes produced slightly different values of z_cl with respect to the ones stated by the authors, such differences are always limited to c·Δz_cl/(1 + z_cl) ≲ 100 km s^-1 and hence the two Gaussian curves of each cluster show the same central values. Our estimates of σ_v agree with within the errors albeit sometimes the distributions are far from being Gaussian, especially for those systems experiencing major merging events (see e.g. SpARCS0035).