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:However, despite the fact that a large body of work has been dedicated to concurrent search data structure (CSDS) algorithms [6, 9, 11, 13, 14, 18, 23, 24, 28, 32, 37, 39, 43, 51, 53, 57, 58], their design and implementation remains an onerous task.
Category: