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 DNA obtained from 14 different isolates was evaluated by amplifying markers commonly used in phylogenetic and population studies: the ITS region (Cooke et al. 2000) and two polymorphic microsatellites, PS36 (Dorrance and Grünwald 2009) and P74-75 (Schena et al. 2008), respectively.
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