The statistics of Sco X-1 kHZ QPOs
  Recently an additional technique was applied to investigate the properties of kHz QPOS, i.e. the analysis of the distribution of frequency ratios or frequencies themselves. I review the results of such work on the data from ScoX-1: Abramowicz et al. (2003), which was later criticized by Belloni et al.(2005). I conclude that the findings of the latter paper are consistent with results presented earlier: kHz QPOs cluster around the value corresponding to the frequency ratio of 2/3. I also discuss the random walk model of kHz QPOs and possible future observations needed to verify it. 
Tomasz Bulik