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 thermoneutral conditions, plasma concentrations of the anti-inflammatory cytokine IL-4 are not changed in response to a marathon run or cycling for 30-120 min (Nieman et al. 2001; Suzuki et al. 2000; Svendsen et al. 2014; Zaldivar et al. 2006).
Category: