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:Taken together with the results of Gagliardo et al. (Gagliardo et al., 2006; Gagliardo et al., 2008; Gagliardo et al., 2009), this result strongly suggests that putative ferrimagnetic receptors in the upper beak, lagena or elsewhere do not play a role in homing of pigeons in this study.
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