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:Previous SPM studies (Salmon et al., 2000; Sakamoto et al., 2002; Kemp et al., 2003) matched the severity of dementia between early onset and late onset groups with MMSE or ADAS-cog (Alzheimer’s Disease Assessment Scalecognitive subscale) scores that reflect only the cognitive aspects of dementia.
Category: