Comparison of the multi-epoch spectra of SN 2013fs at early times with the spectra for models r1w5h (top) and r1w5r (bottom). All spectra have been scaled and shifted; the ith spectrum is normalized to its maximum value within the wavelength range displayed, and then shifted by a constant equal to i × 0.25. There is one ordinate tick mark every 0.5. The observations were corrected for redshift but not for reddening. These two models roughly encompass the properties of SN 2013fs with small offsets in the persistence of some lines (e.g., Ovi 3811–3834 Å). See Sect. 5.2 for discussion.