Double logarithmic plot of expansion velocity in km s^-1 versus turn-on time in days after outburst including error bars. Annotations refer to the time elapsed in days between the outburst and when the optical spectrum was obtained. The red line indicates the best fit from a weighted regression. The red data point represents the atypical nova M31N 2007-10b. The blue data point is nova M31N 2003-08c for which the actual turn-on time is difficult to determine. The grey symbols visualise a generic shift of the expansion velocity by  + 300 km s^-1 for those novae for which spectra were taken more than ten days after outburst. The grey, dashed line shows the best fit after the shift.