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:Temporal trends and age-specific rates were plotted using a semilog scale, with a y- to x-axis ratio of 1 log cycle=40 years, such that an angle of 10° portrayed a change of 1% per year.(22) We aggregated data over years to derive more stable rate estimates.
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