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:This is not only an interesting problem by itself [3], but is also a key component to many potential applications including 3D reconstruction [1, 7, 8], graphical navigation [3, 2], and content-based retrieval [9].
Category: