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:In fact, we were able to explain up to 39% of the ethnic differences in EBV seroprevalences, of which socioeconomic position was the most important contributor, which is in line with previous studies.(42,44) However, it has been suggested that ethnic differences could not be explained by crowding.
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