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:We have previously shown that HMGA1 is a novel target of the ataxia-telangiectasia mutated (ATM) protein (Pentimalli et al., 2008), the main cellular sensor of DNA damage.
Category: