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:Particularly, the visceral tissue volume at 41–50% LTR, which has high conductivity because it is mainly made up of smooth muscle and water, has a low but significant negative correlation between the residual of the trunk SM volume estimates, expressed as a percentage of the trunk SM volume (13).
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