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 average amplitudes of contralateral PBR (cPBR) and ipsilateral NBR (iNBR) were negatively correlated as previously reported and thought to result from increased ipsilateral inhibition occurring concurrently with increased contralateral excitation (Klingner et al., 2010; Shmuel et al., 2002).
Category: