Typical Scales in the Spatial Distribution of QSOs
  We present results of searching for the possible typical scales in the spatial distribution of QSOs. Our method is based on the second derivative of the two-point correlation function. This statistic is sensitive to the scale of the maximum in the spectrum $P(k)$ of the density perturbation in the universe. This maximum or bend scale can be detected as the wavelengths of the periodic component in the second derivative of the integral correlation function. For various QSO samples compiled from surveys of pencil-beam and bright QSOs, a typical scale of about 93 $\pm$ 10 h$^{-1}$Mpc for $q_0=0.5$ has been detected. This typical scale is in good agreement with that found in the spatial distributions of galaxies, clusters of galaxies, and CIV absorption systems of QSOs if $q_0$ is taken to be $\sim 0.2$. Therefore, it is likely a common or universal scale in the large scale structure traced by these objects. This result is consistent with the assumption that the typical scale comes from a characteristic scale in the spectrum of the density perturbation in the universe. 
Zugan Deng, Xiaoyang Xia and Li-Zhi Fang