In the paper of Roberts (2012, GR), the mean curve of εHf(t) is recalculated so that it represents the percentage of depleted mantle input within an available range, with this range being based on the depleted mantle value plus two epsilon units for the maximum, and an evolution line from 4.56 Ga using a crustal Lu/Hf value of 0.015 for the minimum (mantle–input curve in Fig. 1); this mantle input curve is plotted with the mean of the Hf data as zero (Details see in the attachment). However, I still have no idea how to calculate such curve.