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:A novel study employed in situ biotraps with Bio-sep beads amended with 13C-labeled benzene or toluene followed by lipid extraction of the attached microbial community to verify biodegradation by indigenous microorganisms (Geyer et al. 2005).
Category: