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:The maximum residual tensile stress at both locations vary between 0:4 Y and 0:8 Y, in general agreement with experiment measurements (Boyce et al., 2001b; Peters et al., 2002).
Category: