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:The prognosis of FVPTC in our study was excellent, similar to the
results of previous studies (Chan 2002; Yu et al. 2013), and FVPTC is known to have less frequent locoregional recurrence than conventional PTC (Burningham et al. 2005; Lang et al. 2006; Nechifor-Boila et al. 2013), although there…
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