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:These results are consistent with results from prior studies of normal personality traits during different periods in adulthood which suggest that genetic influences are stable over time (McGue et al. 1993; Johnson et al. 2005; Kandler et al. 2010).
Category: