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:Recently, the flgII-28 region in Pst flagellin specifically recognized by Solanaceae species and a new domain other than elf18 in EF-Tu recognized by rice were reported as new MAMPs (Cai et al., 2011; Clarke et al., 2013; Furukawa et al., 2013).
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