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 a review of 65 studies on children's physical activity (ages 3e12) and the built environment, Ding et al. (2011) find that the most consistent correlates with physical activity include access/ proximity to recreation facilities, traffic speed/volume, mixed land use, residential density and…
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