Reichart showed that the light curve of GRB 970228 could only have been caused by a supernova. Definitive evidence linking gamma-ray bursts and supernovae was eventually found in the spectrum of GRB 020813, and the afterglow of GRB 030329. However, supernova-like features only become apparent in the weeks following a burst, leaving the possibility that very early luminosity variations could be explained by dust echoes.