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:These reference genome sequences were used: Arabidopsis thaliana (Ath) TAIR10, Arabidopsis lyrata (Aly [30]), and Arabis alpina (Aal; sequence [18] and gene annotation [18]).
Category: