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:Squalene epoxidase (Sqle, B173-fold increase) regulates one of the final catalytic reactions of
cholesterol biosynthesis (Xu et al, 2005; Clapham and Arch,
2007).
Category: