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:Our classification of comorbidities was also dependent on coded data, which may have inaccuracies but is unlikely to be differentially distributed between RA and non-RA cases, and therefore unlikely to introduce systematic bias into the results [27].
Category: