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:Diffusion weighted imaging (DWI) revealed a higher apparent diffusion coefficient (ADC) in cortical tubers compared to normal-appearing brain, as well as higher ADC values in epileptogenic tubers in comparison to nonepileptogenic tubers [22].
Category: