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:2 system [50] by collecting for each predicted open reading frame observations from similarity searches against sequence databases (nr, SwissProt [3]), KEGG [30], COG [77], genomesDB (see next paragraph), and protein family databases (Pfam [15]) and InterPro [25]).
Category: