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:Their performance is presented in comparison to state-of-the-art methods such as original GNNS [4], EFANNA [6], which is the most effective method in recent studies, FLANN [17], E2LSH [3] and ANN [26].
Category: