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:As we have seen previously in E. coli expressed P450 3A37 (Rawal et al., 2010b), thekinetics of exo-AFBOandAFQ1 formation (1: 6) followed a sigmoidal kinetic Hill model, indicative of positive cooperativity (Fig.
Category: