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:…brain that regulate the periods of behavioral and physiological rhythms, as well as at the molecular level where alcohol has been found to induce changes in the expression of canonical circadian clock genes (Chen et al., 2004; Rosenwasser et al., 2005b; Seggio et al., 2009; Spanagel et al., 2005a).
Category: