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 differential magnitude of effect in large versus small studies (Ioannidis et al.
2003; Zintzaras et al. 2005) for the allele contrast was tested using the Egger regression test for funnel plot asymmetry (Egger et al. 1997) and the Begg-Mazumdar test, which is based on Kendall’s tau (Begg and…
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