Dependence between some spectral and physical characteristics of quasars
  Using 192 composite spectra stacked from subsamples of individual SDSS DR7
quasar spectra binned in spectral index, $\alpha_{\lambda}$, and logarithm of
monochromatic luminosity at 1450 \AA, $\log{l_{1450}}$, we found that there is
a dependence of the emission line equivalent width (EW) on spectral index
(correlation or anti-correlation) for some lines, mostly for those lines for
which the Baldwin effect is detected. We also show that there is no dependence
between the virial mass of the central supermassive black hole of a quasar and
its spectral index $\alpha_{\lambda}$.
