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 similar profile of memory dysfunction has been described between MCI and AD (Petersen, 2004b; Petersen et al., 1999), and in MCI subjects with a higher risk of conversion to AD (Petersen, 2007; Sarazin et al., 2010).
Category: