the literature (see also @Bentz15 for a compilation[^1]). Sources without estimates of host-galaxy contamination to the optical luminosity $L(5100\,{\rm \AA})$ have been excluded. This database provides the fundamental $R$–$L$ calibration for the single-epoch mass scale. In this contribution, we will refer to these collectively as the “reverberation-mapping database (RMDB)”.

2.  Spectral measurements from the Sloan Digital Sky Survey Reverberation Mapping Program [@Shen15 hereafter “SDSS-RM” or more compactly simply as “SDSS”]. We use both  (Table A3) and  (Table A4) data from the 2014–2018 SDSS-RM campaign [@Grier17b; @Shen19; @Grier19]. Each spectrum is comprised of the average of the individual spectra obtained for each of the 849 quasars in the SDSS-RM field.

In addition, because  RM measurements remain rather scarce, we augmented the  sample with measurements from [@Vestergaard06] (hereafter VP06), who combined single-epoch luminosity and line-width measurements from archival UV spectra with -based mass measurements of the objects in Table A1. The UV parameters are given in Table A5; we note, however, that we have excluded 3C273 and 3C390.3 because they both have uncertainities in their virial product larger than 0.5dex; the former was a particular problem because there were far more measurements of UV parameters for this source than for any other 