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:The potential for BCL-xL to modulate other channels in the outer mitochondrial membrane is suggested by the finding that BCL-xL regulates the open state of the mitochondrial voltage-dependent anion channel (VDAC) in synthetic membranes (Degterev et al., 2001; Vander Heiden et al., 2001).
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