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:…by E. coli expressed P450 1A5 and 3A37 support these findings; P450 1A5 produced exo-AFBO and AFM1 (AFB1 concentrations: 2–500 μM) in a ratio of 1: 2, while P450 3A37 produced exo-AFBOandAFQ1 (AFB1 concentrations: 0.1–1000 μM) in a ratio of 1: 6 (Rawal et al., 2010b; Yip and Coulombe, 2006).
Category: