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:Selective knockdown of Cn A and I B abolished the signaling, and caused a reversal of the metabolic properties and invasive behavior in mtDNA-depleted C2C12 cells (Biswas et al., 2003, 2008b).
Category: