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:Shimodaira–Hasegawa tests27 (SH test) and approximately unbiased tests28 (AU; Shimodaira 2002) were performed with Treefinder to test the tree topologies.
Category: