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:D and 3-CB has been confirmed (Kasberg et al., 1995; Laemmli et al., 2000, 2004; Pérez-Pantoja et al., 2000; Plumeier et al., 2002).
Category: