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 evaluation of apoptosis by flow cytometry that was carried out 24 h later revealed an increasing proportion of cells recorded in the sub-G1 phase with increasing concentrations of arachidonic acid (Dymkowska et al., 2006).
Category: