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 reversal component requires orbitofrontal cortex (Dias et al., 1996; Fellows and Farah, 2003; Hornak et al., 2004; Izquierdo et al., 2004; Murray and Izquierdo, 2007).
Category: