Primary facility for traceable measurement of BSSRDF: erratum

An erratum is presented to correct the measurement equation used for the calculation of the BSSRDF in our manuscript [Opt. Express29 (21), 34175 (2021)10.1364/OE.439108]. This correction affects slightly the results showed in Figs. 7 and 8 of the primary manuscript, so they are replaced by Fig. S1 and Fig. S2, respectively, of the current erratum. The discussion on the results of Fig. 7 of the primary manuscript is completely valid also for the new results, but a slightly different discussion is given on the new results showed in Fig. S2. Nevertheless, the conclusions of the original manuscript are not affected at all.