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:Antibodies recognizing mammalian homologs of katanin also recognize large microtubule-dependent structures surrounding γ-tubulin foci at spindle poles in several cell types and, in addition, recognize a smaller microtubule-independent focus at the centrosome in some cell types (McNally and Thomas, 1998).
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