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:Quantitative geneticists have documented numerous cases of such interactions (Stuber et al. 1992; Ragot et al. 1995; Cockerham and Zeng 1996; Melchinger et al. 1998).
Category: