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:Chloroquine and the bovine adrenal medulla peptide 8-22 (BAM8-22) elicit itch-related scratching through MrgprA3 and MrgprC11, respectively, in mice (Liu et al. 2009), and BAM8-22 elicits itch in humans (Sikand et al. 2011).
Category: