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:The network model is similar to the model used in Fierst (2011a, b) and variants of this framework have been developed in a range of evolutionary studies (i.e.,Wagner 1996; Siegal and Bergman 2002; Bergman and Siegal 2003; Masel 2004; Azevedo et al. 2006; MacCarthy and Bergman 2007; Ciliberti et al. 2007a, b; Siegal et al. 2007; Palmer and Feldman 2009; Draghi and Wagner 2009; Espinosa-Soto and Wagner 2010).
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