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:…associated with the tip and kinocilial links of sensory hair bundles in the chick inner ear and the ciliary calyx of photoreceptors in the eye (Goodyear and Richardson, 2003), is an avian ortholog of human protocadherin-15, a product of the deaf/ blindness Usher syndrome type 1F/DFNB23 locus…
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