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:…Takamori et al. (2001)
Endocrine cells, diencephalon (thalamus);
presynaptic
Brainstem catecholaminergic groups
Stornetta et al. (2002a, b); PVN (Herman et al. 2004); ME CRH cells, PP Wittmann et al. (2013)
Not Viable (die at birth)
Moechars et al. (2006), WallenMackenzie et al. (2006)
VGluT3…
Category: