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:To determine whether the intron length or position of intronic binding sites in our CLIP tag set is specific to the species, developmental stage, and/or tissue type, we performed similar analyses on published CELF1 CLIP tags from postnatal mouse hindbrain [24].
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