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:Oral disposition index (DI), a measure of pancreatic b-cell function in response to ambient insulin sensitivity, was calculated as: INS0‚Äì60/GLC0‚Äì60 9 Matsuda index (Abdul-Ghani et al. 2006; Miyazaki et al. 2008).
Category: