Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:We also apply attribute selection and select the most informative 2,000 terms using Information Gain as described in Altınel et al. (2013, 2014a, 2014b), Ganiz et al., 2009, (2011) and Poyraz et al. (2012, 2014).
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