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:…mechanisms of resistance to CDDP have been described, including reduced intracellular accumulation of CDDP; increased detoxification of CDDP by the thiols, glutathione and metallothionein; increased DNA-repair activity; and increased tolerance to DNA damage (Galluzzi et al. 2012; Kelland 2007).
Category: