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:In the last 5 years, it has been published as the most comprehensive study on the distribution of PLCb1 in the mouse brain, showing that it is highly expressed in the somatodendritic compartment of principal neurons of the telencephalon (Fukaya et al., 2008).
Category: