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:MT is also produced as an intermediate of dimethylsulfide (DMS) degradation (Lomans et al., 1999a, 2002; Bentley and Chasteen, 2004; Schäfer et al., 2010).
Category: