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:…of corticospinal projections from the site of stimulation, indexed by reduced amplitude of motor evoked potentials in relaxed hand muscles (Chen et al., 1997; Maeda et al., 2000; Touge et al., 2001; Romero et al., 2002; Tsuji and Rothwell, 2002). rTMS at 1 Hz reduces the amplitude of the…
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