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:Linear subspaces generated from shape and albedo information recovered from a single image: (a) The (re-scaled) first 9 dimensions of an 11D approximation of the illumination cone [8] (b) The first 9 harmonic images [2] (c) Synthesised images of a subject illuminated by lights from the universal configuration [11].
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