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:Moreover, comparable results were obtained in an in vivo imaging study on mice, which was performed with the highly resolving U-SPECT [30]; in this investigation, intraperitoneal application of 2.5 mg/kg amphetamine led to a 27% reduction of [123I]IBZM binding relative to baseline.
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