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:Several fundamental properties are notable in cellular expression and subcellular localization of PLCb1 in the rodent brain (Watanabe et al., 1998a; Nakamura et al.,
d.
2004; Nomura et al., 2007; Fukaya et al., 2008).
Category: