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 our previous study of slow regular saccades, we demonstrated the invariance of saccadic latencies with target angular displacement (Darrien et al., 2001) but had diYculty in reconciling the results with those of previous studies which showed an increase in latency (Fuller, 1996; Kalesnykas &…
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