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:, 2005) and ICSM18 (aa 143–153; Beringue et al., 2004; Khalili-Shirazi et al., 2005) were used to detect PrP.
Category: