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:Previous comparisons of transcriptome content [10], gene expression patterns [11-13], and gene function [14,15] between Amborella and other flowering plant species have suggested that much of the floral development program that has been characterized in Arabidopsis, snapdragon and maize existed in the last common ancestor of extant angiosperms.
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