Lyα transmission in the spectrum of GRB 130606A (squares). Lyβ (diamonds) and Lyγ (crosses) measurements are converted to equivalent values at Lyα. The small black triangles, diamonds, and the grey squares are measurements based on quasars from Fan et al. (2006), Goto et al. (2011), and Songaila (2004), respectively. The solid line is the best power-law fit to the data at z< 5.5 by Fan et al. (2006, their Eq. (5)). The uncertainties of the QSO points are typically a factor of two.