Comparison of our GRB 100621A sub-mm light curve to previous sub-mm observations of GRBs with more than one observation, and selected upper limits for a few famous GRBs. Different symbols mark different observer frequencies, and colours denote different GRBs (except for the upper limits). Data are from GRB 030329: Kohno et al. (2005); Sheth et al. (2003); GRB 090313: Greiner et al. (in prep.); GRB 080129: Greiner et al. (2009b); GRB 090423: Bock et al. (2009); GRBs 091102, 110709B, 110715A, 100901A, and 110918A: de Ugarte Postigo et al. (2012).