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 this study, according to the method described by Williams and Rakic (1988) and West and Gundersen (1990), we observed the pyramidal cells and dentate granule cells in the cross sections of the middle portion of a hippocampus that had been sliced into 60 cross sections, 8 lm thick per section.
Category: