evidence for redshift quantization in a sample of 1647 galaxy-quasar pairs from the 2dF Galaxy Redshift Survey: "Given that there are almost eight times as many data points in this sample as in the previous analysis by Burbidge & Napier (2001), we must conclude that the previous detection of a periodic signal arose from the combination of noise and the effects of the window function." In response, Napier and Burbidge (2003) argue that the methods employed by Hawkins et al. to remove noise from their samples amount to "excessive data smoothing" which could hide a true periodicity. They publish an alternate methodology for this that preserves the periodicity observed in earlier studies. In 2005, Tang and Zhang found no evidence for redshift quantization of quasars in samples from the Sloan Digital Sky Survey and 2dF redshift survey. Arp et al. (2005) examined sample areas in the 2dF and SDSS surveys in detail, noting that quasar redshifts: "... fit very closely the long standing Karlsson formula and strongly suggest the existence of preferred values in the distribution of quasar redshifts." A 2006 study of 46,400 quasars in the SDSS by Bell and McDiarmid discovered 6 peaks in the redshift distribution consistent with the decreasing intrinsic redshift (DIR) model. They conclude that this correlation is unlikely to be a selection effect, given the method used to determine intrinsic redshift relations. Schneider et al. (2007) and Richards et al. (2006) report that the periodicity reported by Bell and McDiarmid disappears after correcting for selection effects. However, Bell and Comeau (2010) have since argued that this correction removes nearly half of the sample and does not explain how selection effects give rise to redshift peaks. The same study also concludes that a "filter gap footprint" renders it impossible to verify or falsify the presence of a true redshift peak at Δz = 0.60. A 2006 review by Bajan et al. discovered weak effects of redshift periodization in data from the Local Group of galaxies and the Hercules Supercluster. They conclude that "galaxy redshift periodization is an effect which can really exist", but that the evidence is not well established pending study of larger databases. A 2007 absorption spectroscopic analysis of quasars by Ryabinkov et al. observed a pattern of statistically significant alternating peaks and dips in the redshift range Δz = 0.0 − 3.7, though they noted no statistical correlation between their findings and