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:, 2011 [11] Reconstruction of severe tibial shaft fractures Free vascularized fibula or osteocutaneous fibular flap Tibia 38 Good outcome with mean healing time of 21 weeks in 31 cases and of 32 weeks in 7 patients
Category: