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:Manganese superoxide dismutase, fibronectin ELISA and SIRT1 enzyme activity assay Manganese superoxide dismutase (MnSOD) and fibronectin (FN) ELISAs were performed using commercially available kits [26, 43].
Category: