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 cells, grown on 25-mm coverslips, were loaded with rhodamine 123 (R123, Molecular Probes) by incubation with 10 mg/ml for 30 min at 37°C (11, 12).
Category: