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:…shown to be difficult to measure and studies have found conflicting results regarding the locations of peak shear pressures beneath the foot (Pollard et al., 1983, Tappin and Robertson, 1991, Hosein and Lord, 2000, Perry et al., 2002, Yavuz et al., 2007, Stucke et al., 2012, Mori et al., 2012).
Category: