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:The last fragment has also been widely used to elucidate
phylogenetic relationships among taxa from several plant families (Stedje 1998; Doust and Kellog 2002; Goldblatt et al. 2002).
Category: