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:Work with non-neuronal cells has suggested that BCL-xL regulates the flux of metabolites across the outer mitochondrial membrane to facilitate transport of ATP into the cytosol after a death stimulus (Vander Heiden et al., 2000, 2001).
Category: