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:, metabolic state, changes in hepatic clearance of acyl-ghrelin, differences between acyl-ghrelin and unacylated ghrelin clearance rates, availability of substrate (octanoate/octanoyl-CoA) and/or changes in GOAT activity [61, 62, 65, 66].
Category: