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:For example, studies of genetic correlations in Drosophila frequently report positive correlations among most traits measured (Cowley and Atchley 1990; Wilkinson et al. 1990; Norry et al. 1997).
Category: