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:Case patients were included in the study if they had an episode of pSAB, defined as bacteremia for longer than 7 days.(3) For patients with multiple episodes of pSAB, only the first episode of SAB in each patient was included for analysis.
Category: