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:SSA responses have also been discovered in auditory thalamus (Anderson et al., 2009) and auditory cortex (Von der Behrens et al., 2009; Ulanovsky et al., 2004, 2003).
Category: