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:In the CAPOA algorithm, occlusion detection is based on image blocks, not individual pixels as is done in [7], [8], [23] and [24], because spatial context plays an important role in deciding whether a target is occluded.
Category: