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:cilial links of chick hair cells and the calyceal processes of photoreceptors, immunoprecipitates two proteins of 200 and 250 kDa from chicken retina (Goodyear and Richardson, 2003).
Category: