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  \subsection{The Liu Quasar Pair Catalogue}  Summarize main The data sample used in this project is obtained from Lui et al 2011. The purpose of the criteria adopted by Lui in selecting data  points for the Quasar Pair Catalogue is to refine the AGN sample  from section 2.2. the parent sample to a sample of interacting AGN pairs only.   AGN pairs that make up the parent sample are identified optically from the spectroscopic sample of the SDSS DR7. Lui et all 2011, answers the question: are all the AGN pairs  in Liu the parent sample to be included in the study? Using line of sight (LOS) velocity differences (or offset) and transverse separation, rp ,Lui selects only AGN pairs that are interacting.  The choice to use projected separations rp < 100h70-1 kpc to refine the sample space – remove pairs that are closely separated but are not interacting. Lui further observes that most pairs with separation greater than 100 kpc are found to be closely separated but not interacting with one another. Selecting those with separation less than 100 kpc helps remove these points that are not a part of our sample space. It is surprising to note that 100 kpc is larger than the thresholds used in other galaxy pair studies namely (Barton  et al. 2011 2000; Ellison et al. 2008; Darg et al. 2010), but lui does not explain why 100 kpc is used as the threshold.  Lui further Justifies the use a LOS velocity offset (Δv) < 600 km s-1 as a method to further refine the desired sample space. Observing the distribution of (Δv) of AGN pairs (figure (2) provided in Liu) shows us that that most AGN pairs are found within the 300 ≲ (Δv) < 600 km s-1 interval. Even so, Lui et all further states that Δv range within which the pair is still interacting depends on the environment – there could be a chance that some data point were erroneously cut from the sample.  Visual inspection of SDSS images for spectroscopically selected images further removes 34 AGN pairs from the parent sample. Perhaps their spectroscopic profiles do not match those of interacting pairs. What was the criteria for this- is still left unanswered.  Lui also notes possible outliers and common trends in our refined sample space. The surprising, sixteen data points with z> 0.16 ,which seem to be outliers are kept in our sample. They are said to reduce uncertainties at higher red-shifts.   Lui notes that corrections are to be made to the sample due to SDSS’ limitations, as pairs with angular separation ≤ 55” lead to the spectroscopic data of the pair not being captured unless one of the AGN is captured on an overlapping plate . The correction is done by supplementing the observed pairs (with angular separation≤ 55” ) with modified ([C-1]Np) pairs. The Np pairs are randomly drawn from the sample pairs with separation smaller than 55”. details of this correction are contained in Liu et al 2011.