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:…on cells of the CA1 subregion (Barnes et al., 1997; Shen et al., 1997; McEchron et al., 2001; Rosenzweig et al., 2003) or have combined the data obtained from the CA1 and CA3 subregions for analytical purposes (Tanila et al., 1997a; Oler and Markus, 2000; Wilson et al., 2003, 2004, 2005).
Category: