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:It should be noted, however, that a similar study of the metabolites of tamoxifen led to the identification of putative metabolites that are mutagenic (Cunningham and Rosenkranz 1995; Cunningham et al. 1995).
Category: