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:Solutions to the PnP or PnL problem cover only single-view perspective cameras, hence new methods are needed to efficiently deal with the multiview PnP (NPnP) problem [3, 8, 11, 12].
Category: